Creating/modifying registration process

Hi All

Not sure if this is the right place to post this question but here is what I am trying to do:

I need to customize the registration process and get the user to select certain options related to our service to them, location, have a customized background and wizard-like process.

The problem is that I am not sure where to begin. I need direction for this development. is it a plugin? if so, can I modify one, which one?

Please give me a hand.