It's a 17 year old car. It's GOING to nickle and dime you. It just will. Especially as a VW.
That motor is good but it's not unheard of for them to eat cam followers (lifters? followers? that part) at these miles. And the timing belt must be done with absolute precision. If VW says a bolt needs replacing--they're not kidding. This is an interference motor and if the belt breaks, it bends valves. Period. Reman heads start at like $1,500 and then you redo the timing belt job (price off the top of my head).
Glowplug harnesses are kinda hit and miss; as long as you don't mind replacing them it should not be a problem. If it is 99.5 or later (I forget if Golf did that half year thing) then the areas behind the front finder liner, next to the rockers, is a known dirt trap, and will rot the rockers starting there. The car is very good at resisting rust underneath, but not this area, due to dirt. Likewise, 99.5+, the rear axle slowly bends over time, leading to a toe-in condition which causes rapid feathering if frequent tire rotation is not done.
I forget now; at some point VW used 60k belts and then went to 90k belts--but in order to go 90k you must use all the 90k parts. It is possible to use 60k parts (and it's possible to use cheap parts that won't go the distance--see above).
Clutches and turbos do die on these. Upgraded clutches are common, and recommended, so as to allow bigger and better turbos. Injectors don't last forever either; many swap nozzles for more power. "Chipping" is common too, as more fuel really wakes up these motors.
In the USA mechanics (especially dealers) used to be clueless about these cars. Canada was better off. Usually the first advice from TDI owners to prospective buyers was to figure out who their local TDI guru's were.
On the flip side, it's a common chassis with rabid followers and decent parts support. If it's a decent car and you have a few grand set aside for repairs it can be a great ride, if you like turbodiesels. If you want something that never breaks (and is dirt cheap to repair at a mechanic if it does), then run away. Far away.