You can find great repair manuals with step-by-step instructions, diagrams, parts locations and other important information here: http://www.eautorepair.net/Marketing/Default.asp?VID=125669
I wouldn't start without it, it's not a simple process.
Zee
RepairPal Certified shops can diagnose and repair your 1991 Audi 100. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.