Never owned one, but my cousin owned a newer TDI about a decade ago. They let me test drive it while they rode in the back and I drifted it around a corner without their permission. Oopsie. Sorry not sorry. That car drove great and had incredible torque (shockingly, they now own a Tesla!).
Everything I've heard is that they are cars for people who like to tinker on cars. You buy a VW for the driving dynamics, not the reliability, economy, or durability. You love it so much you put in that head gasket, the new transmission, the new radiator, the alternator, the blah blah blah and it's just a lifestyle. "German engineering" means a simple function like a door latch or water pump that should have 3 parts has 15. You threaten to quit it, drive a Civic for a few months, experience tremors in your hands, sell the Civic, and you're back at rock bottom again, looking on some ancient forum about how to remove the entire rear suspension assembly to reach the fuel pump.
Now, at 21 years old and 265k miles, you have REALLY purchased the lifestyle!
That said, there's not much you can buy for $3300 that is reliable and not close to needing an engine or transmission overhaul. A $3300 Toyota is not necessarily a reliable vehicle either. You do not typically get "clean" for $3300 either.
I think your friend gave you a "good" price, not a steal, given the mileage and antique status. His receipts and records should always stay with the car, because you or a future buyer/owner will be referring to them to figure out how much of the car has been replaced and how much is left to replace. This will be important as each big ticket item comes up, and a judgment call must be made.
As others noted, you MUST be capable of doing your own work or this lifestyle will cost more than leasing BMWs. You must also be capable of enjoying this sort of work, or the lifestyle will be miserable. Yet with those two conditions met, the Jetta could provide you a quite satisfying commuting experience that doesn't break that bank.
The real problem with your lifestyle at the moment is that expensive truck. It will keep depreciating and sucking down insurance payments even if you aren't driving it. If you like the Jetta, keep the Jetta. But almost nobody needs an expensive truck because an expensive truck is too expensive to do any work. Yours is too expensive to even drive to work! In the worst possible year, when the Jetta needs a new engine AND transmission, it won't cost you as much as such a truck usually depreciates.