Yeah, that's not as bad as some quotes that have been posted on here from Audi in the past though.
You'll be fine. End of the day, it's 2 x 10mm bolts and a hose clip! Undo the hose clip and pull hose off. Allow coolant to drain out.
Top bolt is easy, bottom one requires a small spanner or 10mm socket with a universal joint and I admit is a fiddly ******. Can be made easier by removing alternator wiring (recommended - just don't forget to refit).
Pull plastic pipe off, pull old thermo out. Throw away. Fit new thermo the same way the old one came out. Secure with either a) new O ring (if using new, wipe it over with used coolant first) or b) old O ring.
Put plastic pipe back on. Put top bolt in to secure but don't tighten up too far yet, swear a lot as you try to get bottom bolt back in. Get it in eventually. Do both bolts up. Re fit alternator wiring. Refit hose.
Slap G12 in header tank until at bottom of sensor. Leave cap off header tank. Start engine. Top up header tank as required with water. Check for leaks. Turn heaters on 'HI' and fans on full. Check coolant level again. Leave for 2 mins. Put header tank cap on. Let engine warm to operating temp. Check coolant level again.
Done.