Hello. I was hoping for some veterans to help guide me through a process of what i'm trying to implement on my site. I use the basic shopp api plugin, most recent version.

Long story short, I have a one product website, where the payment portal issues a login id and password for my client.

What i want to end up from my checkout was something along these lines:
step 1- form which inserts customer data into my db and sets customer status="inactive". on submit, redirect to add cart item and proceed checkout
step 2 - enter billing information and submit to payment gateway
step 3 - on payment success, send receipt to email

Here is what I must currently do, under step 3:, on success, update my customer database for customer status="active" where the customer will be matched through billing email. then I must generate an additional letter to my customer stating the account is ready to be used. - There will be more functionality added to this later. but this is general gist.

Can someone guide me with where to insert these lines of code, and what to modify to allow this to happen.

Also, if there is a simple way for a variable to be passed through the url, i can use a _GET statement to do the necessary code in simple php if someone can help me put it in the right file. I'm somewhat of a wordpress n00b. Thank you for your help