I cant say much for the TDi since I had a 1.8T that was heavily modded for several years. I would make sure the normal things are there. maint. records and the like. that there is not any obvious issues mechanically.

The MkIV interiors normally need some loving after the 100k mark. Check to see the recall had been done on the sunroof drains. That there has not been any really bad leakage where the fabric and stuff is starting to come off.