How can I add fadeIn and fadeOut with a duration that I can set/adjust to this javascript?
The site is using Zencart and the the Image Hover effect comes from the Image Handler 2 Add-on.

Thank you in advance for your help. Your time and attention in helping me with this is greatly appreciated.

Here is a link to the site residing on a subdomain I use to build sites on http://test3.fullspecweb.com

I read the "Read Before Posting" and it said to only post the code you are having trouble with, but I have no idea which section that would be so I apologize for being such a noob

Here is the script from the jscript_imagehover.js file...
Code:
var offsetfrommouse=[20,20]; //image x,y offsets from cursor position in pixels. Enter 0,0 for no offset
var displayduration=0; //duration in seconds image should remain visible. 0 for always.
var currentimageheight = 400;    // maximum image size.
var padding=10; // padding must by larger than specified div padding in stylessheet

// Global variables for sizes of hoverimg
// Defined in "showtrail()", used in "followmouse()"
var zoomimg_w=0;
var zoomimg_h=0;
var vpos;
//Detect IE
var stIsIE = /*@cc_on!@*/false;
//detect opera
var isOpera =
    window.opera?1:0;
// Detect Webkit browsers
var isWebKit =
  navigator.userAgent.indexOf("AppleWebKit") > -1;

if (document.getElementById || document.all){
  document.write('<div id="trailimageid">');
  document.write('</div>');
}

function getObj(name) {
  if (document.getElementById) {
        this.obj = document.getElementById(name);
    this.style = document.getElementById(name).style;
  } else if (document.all) {
    this.obj = document.all[name];
    this.style = document.all[name].style;
  } else if (document.layers) {
    this.obj = document.layers[name];
    this.style = document.layers[name];
  }
}

function gettrail(){
  return new getObj("trailimageid");
}

function truebody(){
if (isWebKit){
  return document.body;
  }else if (isOpera) {
  return document.documentElement;
  }else{
  return (!window.opera && document.compatMode && document.compatMode!="BackCompat")? document.documentElement : document.body
  }
}

function showtrail(imagename,title,oriwidth,oriheight,zoomimgwidth,zoomimgheight, image, startx, starty, startw, starth){
    zoomimg_w=zoomimgwidth;
    zoomimg_h=zoomimgheight;
  if (zoomimgheight > 0){ currentimageheight = zoomimgheight; }
  trailobj = gettrail().obj;
  trailobj.style.width=(zoomimgwidth+(2*padding))+"px";
  trailobj.style.height=(zoomimgheight+(2*padding))+"px";
  trailobj.setAttribute("startx", startx);
  trailobj.setAttribute("starty", starty);
  trailobj.setAttribute("startw", startw);
  trailobj.setAttribute("starth", starth);
  trailobj.setAttribute("imagename", imagename);
  trailobj.setAttribute("imgtitle", title);
  document.onmousemove=followmouse;
}

function hidetrail(){
  trailstyle = gettrail().style;
  trailstyle.visibility = "hidden";
  document.onmousemove = "";
  trailstyle.left = "-2000px";
  trailstyle.top = "-2000px";
}

function followmouse(e){

  var xcoord=offsetfrommouse[0];
  var ycoord=offsetfrommouse[1];
if (stIsIE){
  var docwidth=document.all? truebody().scrollLeft+truebody().clientWidth : pageXOffset+window.innerWidth-15;
  var docheight=document.all? Math.min(truebody().scrollHeight, truebody().clientHeight) : Math.min(window.innerHeight);
}
else
{
  var docwidth=pageXOffset+window.innerWidth-15;
  var docheight=Math.min(window.innerHeight);

}
  var relativeX = null;
  var relativeY = null;
  if (typeof e != "undefined"){
    if ((typeof e.layerX != "undefined") && (typeof e.layerY != "undefined")) {
      relativeX = e.layerX;
      relativeY = e.layerY;
    } else if ((typeof e.x != "undefined") && (typeof e.y != "undefined")) {
//      relativeX = e.x; // original code replaced to work with Opera
//      relativeY = e.y; // original code replaced to work with Opera
      relativeX = event.offsetX;
      relativeY = event.offsetX;
    }
    if (docwidth - e.pageX < zoomimg_w + (3 * padding)) {
      xcoord = e.pageX - xcoord - zoomimg_w - (2 * offsetfrommouse[0]);
    } else {
      xcoord += e.pageX;
    }
    if (docheight - e.pageY < zoomimg_h + (2 * padding)){
      ycoord += e.pageY - Math.max(0,(0 + zoomimg_h + (5 * padding) + e.pageY - docheight - truebody().scrollTop));
      // returning different values for ff and (opera and webkit) - fixed 12th june 2010
    } else {
      ycoord += e.pageY;
    }

  } else if (typeof window.event != "undefined"){ // Seems to be IE
    if ((typeof event.x != "undefined") && (typeof event.y != "undefined")) {
      relativeX = event.x;
      relativeY = event.y;
    } else if ((typeof event.offsetX != "undefined") && (event.offsetY != "undefined")) {
      relativeX = event.offsetX;
      relativeY = event.offsetY;
    }

    if (docwidth - event.clientX < zoomimg_w + (3 * padding)) {
      xcoord = event.clientX - xcoord - zoomimg_w - (2 * offsetfrommouse[0]);
    } else {
      xcoord += truebody().scrollLeft+event.clientX;
    }
/* event.clientY is not valid in firefox netscape or opera, but ie has to use it */
var ie_offset = -20;
    if ( docheight - event.clientY < zoomimg_h + (2 * padding) ){
      /*
    ycoord += event.clientY - Math.max(0,(0 + zoomimg_h + (5 * padding) - (docheight + truebody().scrollTop -event.clientY) ) );
*/
        ycoord += ie_offset + truebody().scrollTop + event.clientY - Math.max(0,(0 + zoomimg_h + (2 * padding) - (docheight - event.clientY) ) );
    } else {
        ycoord += ie_offset + truebody().scrollTop + event.clientY;
    }
  }

  trail = gettrail();
  startx    = trail.obj.getAttribute("startx");
  starty    = trail.obj.getAttribute("starty");
  startw    = trail.obj.getAttribute("startw");
  starth    = trail.obj.getAttribute("starth");
  imagename = trail.obj.getAttribute("imagename");
  title     = trail.obj.getAttribute("imgtitle");

  // calculate and set position BEFORE switching to visible
if (stIsIE){
  var docwidth=document.all? truebody().scrollLeft+truebody().clientWidth : pageXOffset+window.innerWidth-15;
  var docheight=document.all? Math.max(truebody().scrollHeight, truebody().clientHeight) : Math.max(document.body.offsetHeight, window.innerHeight);
}else{
  var docwidth=pageXOffset+window.innerWidth-15;
  var docheight=Math.max(document.body.offsetHeight, window.innerHeight);
}

  if(ycoord < 0) { ycoord = ycoord*-1; }
  if ((trail.style.left == "-2000px") || (trail.style.left == "")) { trail.style.left=xcoord+"px"; }
  if ((trail.style.top == "-2000px") || (trail.style.top == "")) { trail.style.top=ycoord+"px"; }
  trail.style.left=xcoord+"px";
  trail.style.top=ycoord+"px";

  if (trail.style.visibility != "visible") {
    if (((relativeX == null) || (relativeY == null)) ||
      ((relativeX >= startx) && (relativeX <= (startx + startw))
      && (relativeY >= starty) && (relativeY <= (starty + starth)))){
      newHTML = '<div><h1>' + title + '</h1>';
      newHTML = newHTML + '<img src="' + imagename + '"></div>';
      trail.obj.innerHTML = newHTML;
      trail.style.visibility="visible";
    }
  }
}