The upper a-arm boot seems to be the same as Auti PN: 431.407.377A

It can be done and is not technically difficult but still a real pain in the ass job. Get the boots from your favorite vendor or an Audi dealership (P/N 431.407.377A). The boot is held on with two spring loops. The small end is a single loop round wire and is relatively easy. the big end is a flat wire spring much like a key ring and is the pain in the ass part. What makes it difficult is you need to replace the grease (90 wt.) and it's almost impossible to get the lower spring on without getting the grease on your hands and the outside of the boot, making everything slip out of your grasp. Use a cotter pin puller, or a hook scribe or a piece of wire to pull the lower spring around while keeping it in the groove of the new boot. It helps to have three hands or a helper if your if not so equipped with the third appendage.

Jim Mayzurk

The Audi retainers I bought are both flat wire. The trick to making less of a mess is to just put a little grease on the ball for basic lube, but not any in the boot. Get one of the grease gun needle kits. Once the retainers are on, push the boot down like it will be with the spindle installed and slide the needle in the top off the boot along the shaft and add some grease. Wobble the joint, then do the same on the opposite side.