If your handy with tools go for the Blauparts Kit and tool rental.

If it is a C5, I believe you'll need to put the front end in the service position to get enough room to work, but someone else will need to help you with that cause I am playing with a a C4

 

Not really... It should be a bit easier than a 2.7t (no tubing to and from the turbo's to mess with) and most 4.2's.

If it was me, I would:
1. Buy the kit and rent the tools. (I would ask how long I can keep them... see below.)

2. Get a manual. I like paper but the computer version seem to have more "stuff."

3. Make sure you have a good set of "common tools."

4. Find a good place out of the weather and get something else to drive for the next month or so... (I am MUCH slower than most! See below.)

5. Set aside the next few weekends... not that I would be working on it all the time! (see below.)

6. Stock the fridge with beer... for when you are frustrated or need help. (You have more friends when you have beer!)

 

it's pretty simple. i was mostly worried about taking my bumper off when i was getting started but it comes off easy. The blau kit has pretty good paper directions, that is all that i used. and you can always google anything else you might not understand. Going to need a variety of tools also. seems like EVERY bolt usses a different size


might even wanna do your valve cover gaskets.... i wish i would have, mine are commonly leaking

 

Here is an overall decent writeup.

http://www.audiworld.com/tech/eng39.shtml

But the only thing that I would do different is to use the cam lock bar the the crank locking pin as supplied by the blauparts tool kit rental. Also get the enhanced kit with the timing belt tensioner while at it. Yes it is about $100 more but I heard many cases where the tensioner failed after the new belt installation.

Blauparts kit (as you already know) comes with a pretty decent instruction. One other thing to keep in mind is to pretension the tensioner before locking the cam gears tight. And while at it, replace the front cam seals too. It takes additional 15 minutes.

All and all, I say budget about 10 hours. Oh, one more advise... any plastic parts, including vacuum lines, water line connector and etc become really brittle. So be careful when you are removing any of them. Otherwise you will be paying a visit to the dealer the stealer. Have fun.

 

A 1999 A6 2.8L may be similar to your 2.8L timing belt:
http://www.audiworld.com/tech/eng39.shtml