Depends which coilpack is gone - but even the hardest one only took me 8mins to do (i timed it) - and that was in the pouring rain!
The coilpack I got last week (revision R) - #06B 905 115 R - cost me £29.90 inc. VAT from the local VW garage.
EDIT: Hardest bit for anyone without VAG-COM would be to figure out which coilpack is faulty. Otherwise, it's disconnect cable, pull up carefully (don't wiggle) and replace.
Cylinder 4 is under a vac-reservoir and bracket which requires a 5mm allen-key to remove the 3 bolts, and a 13mm spanner to remove the reservoir.