WARNING: This page is about a different car, the 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Removing And Installing Securing Ring
Courtesy of VOLKSWAGEN UNITED STATES, INC.
Clamp flange shaft in vice using soft jaws. Press out old circlip from groove in flange shaft use new circlip -A-.