It's not "technically" difficult, just a bit of a pain. I've only removed my pump so far, waiting for the replacement to arrive.
Procedure:
1. Jack up the right hand side of the vehicle and place on axle stand I used a large wooden block under the wheel) - just to gain better access from underneath and also improve the height when working from the top.
2. Pop up the headlights, switch off ignition then remove fuses 40 and 41 (to save draining battery power).
3. From the top remove the power feed and then the two reservoir mounting bolts, one clamping at the top of the wing and the other clamping onto the bracket further towards the engine. (10mm socket)
4. From underneath remove the mounting nut/bolt/washers/spacer (10mm) to allow room to wriggle the pump upwards in the reservoir groove. This is quite fiddly getting spanners and hands up enough, hence raising the car at the right hand front.
5. Next very fiddly bit (in my case), remove the jubilee clip (more like a motorbike fuel pipe clamp) - this required a long flat screwdriver and a soaking in WD40 - BUT the nut was also turning, so it was a real pain! I managed to get in there with an open ended 8mm spanner to hold the bracket type thing on the nut side of the clamp that was spinning, then also contort enough to use the screwdriver to undo the clamp totally. Got there with this after approx. 20 minutes sweating...
6. Pull off the water hose - again, pain as there's not loads of room - but with a bit of careful levering on the end of the pipe too it came off. not too hard overall.
7. From underneath, force upwards the pump - not easy as it was a tight fit (a good thing to keep a good seal on the shaft going into the reservoir). In reality I had to put back in the mounting bolts loosely, to hold the reservoir firmer, but once the pump raises a bit they need removing again to allow the sticky out bit that the pipe goes onto to clear the chassis member. A bit fiddly but not too bad.
Hopefully Friday eve I'll just reverse this procedure, with less hassles due to new clamp etc....
Overall, not difficult, just fiddly at times particularly trying to get the knackered clamp off! as mentioned in my other post (before I found this and re-ignited it) the replacement part number I've ordered (2nd hand via eBay) is Audi 357955613 (£13 'ish).
