If you have access to the donor car, make a template of the shifter hole size and location. Get the shifter base plate, boot and M6 TQ arm mount with bolts. Look at the M6's TQ arm too. I think they were reinforced for LT1 M6 cars.
If you don't have it already, get a Factory Service manual. You will need to compare the wiring differences with the Park/Neutral safety switch, Clutch safety switch, Cruise control and Back up lights.
The cable that runs from the P/N Safety switch to the steering column, you can wire tie that "closed" and leave it there......otherwise the steering column will need to come out to remove it.
Loosen the A4's dipstick tube before you drop the tranny.
Remove the lines that run to the radiator. There are little C clips that hold these lines to the tranny.
Place the pedals against the firewall and mark your hole for the clutch cylinder before drilling/cutting.
Remove the steering shaft before trying to push the hydraulics through.
When I did this swap on my wife's 2000 Trans Am last year, I swapped out the Engine/Transmission wiring harness too. (I had the donor car sitting side by side) This may not be feasible for you and you may run into more wiring issues that I didn't.
If your a big guy.....get a little friend to help with the work under the dash. My wife helped
Give yourself PLENTY of time. at least 2 full days. Buy Beer for the end of each day