Well, the typical, such as changing fuel filters, air filters, cabin filters (maybe not), oil filters, engine oil, transmission fluid/oil and blinker fluid is basically the same on all vehicles as well as replacing batteries, starters, alternators, etc. Beyond those, are things like rotors, CV Joints, ball joints, sway bar bushings, and "sometimes" before 400k miles, front and rear wheel bearings that are also pretty typical of a 20 year old vehicle (shock absorbers too). As for the TDIs thru 2006, the 100k mile Timing Belt job, which includes a number of other things, is a challenge for most who generally let a guru do the work, if they can find one. Nope, you don't need to begin hand wringing at 75k miles.... even at 5 or 6 years. (yeah, that DMF will sooner or later be problematic)
My son owns my ol' 2000 Jetta with 388k on it. A couple of weeks ago I replaced the transmission due to 5th gear issues (a story in of itself). I own my brother's ol' 2003 with the engine from his formerly owned 2001 (which got T-boned). Everything works, including the AC. I drive it weekly where or when I don't want to drive our Tiguan 4-motion. The TDI gets double the fuel economy as the Tig.
Fortunately for me, I always had access to my uncle's automotive garage ..... did all my own maintenance there. When I retired, I built a small garage for my tinkering and hobby VW maintenance. I'm the only person in probably 75 to 100 miles with VCDS and that does work on MKIVs. But, like others, I'm in the process of winding down ........ COVID never treated me well and age is catching up too!
Lastly, I enjoyed the cheaper price of Diesel Fuel in my VWs from 1980 thru 2005 when the price went above RUG. Today, at more than a dollar per gallon above RUG, and many places a $1.25 or more, well, it isn't fun any more ,,, in fact, it sucks other than with the ALH in my 84 Vanagon which gets almost double the MPGs of the OE gasser engine (and, oh the torque).
Oh, I don't recommend a TDI to anyone either, as likely they will be calling me to do work on it ... The heyday of the TDI in North America is in the rear view mirror .. sadly.