I did mine the other day. Your BEW TDI starter should only be replaced with a quality new, not remanufactured, starter. The higher compression of the engines likes to eat cheap starters. Heres a hint, local chain parts stores don't carry the starter you need. I won't plug a site to order from but buy it from the dealership or find in the tdi forums where people recommend ordering one from. Yes, they're expensive but you won't be doing it again in 9 months.
Time required is about an hour, probably less if you're comfortable under the hood. I found it was easiest to mostly work from the top side under the hood and removed the battery box and air box to get better access.
Be sure you know how to get the pigtail clips loose on the VW before you start, they're different than most other manufacturers. you release the clip THEN pull instead of most others are release the clip while pulling.