how do I put a fully functional shopping cart feature on a website, and how do I make all the actual transactions happen, also who do I make a web form that people can fill out.

I'm not certain how to put the shopping cart on. You might want to try hotscripts.com
What did you want on your webform?? What kind of back end are you running?

I think you'll want to put this post in the coding section of Webmaster-talk. Most of us geeks hang out over there