I can't really see what would need to be done - paypal basically just requires you to make some magic urls that follow a very simple syntax and need the following information:
* your paypal merchant id (a fixed number)
* your product price
* your product code (optional and totally up to you)
* weight (optional)
and maybe a few other optionals. donations are even simpler
The paypal documents describing this are:
buy now links : http://www.paypal.com/cgi-bin/webscr?cmd=p/xcl/rec/singleitem-intro-outside
shopping cart : http://www.paypal.com/cgi-bin/webscr?cmd=p/xcl/rec/sc-intro-outside
donations : http://www.paypal.com/cgi-bin/webscr?cmd=p/xcl/rec/donate-intro-outside
