My 1998 Passat turns 14 in May of this year and just hit 150,000 miles. Never had a major repair or failure, though suggested maintenance can be costly when timing belts etc. are due to be changed. It's a manual and has the original clutch and transmission. I live less than a mile from the dealership, and get a free loaner car (there is an Enterprise counter at the dealer) when I have servicing, so I've never searched for a less expensive VW specialty mechanic. The latter is a good choice if one is close by and if you have alternate transportation options.
The engine is the 1.8T (still used in some VWs, though now it's a 2.0T), the chip of which was reprogrammed to increase turbo boost so that it gets about 205 HP at the wheels, instead of the stock 150 HP for the 98 models. At the time, VW only offered one other engine choice for Passat, a rather lackluster V6 making 190 HP. The 1.8T was offered in 170-180 HP versions in other VWs (Jetta, GTI, etc.), leading fans of the car to suspect that the engine was "de-tuned" (tuned to the low end of its HP potential) so as not to compete with the V6. In later models, the same 1.8T engine was up-tuned to get 170-180 (the same engine, when coupled with a larger turbo and intercooler, made 225 HP in the Audi TT).
As whirlpool suggested above in his Lincoln Towncar post, what will eventually do the car in is not the drivetrain, but the declining availability of off-the-shelf replacement parts (and this isn't a collectible car, so it's not worth paying way more to have stuff custom made). I recently had this problem with the rubber door gaskets. Two of the three were shot. In the rear doors, the cloth trim along the top of the space for the door (ie between window and roof liner) is part of the door gasket, and the cloth began to separate and droop, no way to repair it. I was able to find the replacement parts (which weren't all that expensive, maybe $50 each) and had them replaced at an auto interior specialist. On the driver door, the rubber was starting to wear away because the sill is sort of high, and after years of my right foot rubbing against the gasket where I exit the car, the rubber began to wear away. This part is no longer available, but the interior guy was able to make a patch from the rubber being discarded from the rear door gaskets. It works but doesn't look stock.
A year ago, the glove box latch broke, so that I could no longer keep the box closed. Unfortunately, they didn't sell just the door or latch, you had to buy an entire new glove box plus door/latch, which cost about $250 in parts alone. However, driving around with a glove box that won't stay closed is a safety issue (makes car look as if someone broke into it) plus it makes it hard to have a front seat passenger. All of the interior trim is fine at this point, but if something goes, sooner or later I won't be able to replace it. [note: they did sell separate doors for newer models, but not for a 98, and the box had been redesigned since 98, so that a door for a newer model would not fit my glove box; as a result, both box and door required replacement].
The only thing I've never bothered to repair is the cruise control. The switch is broken, and in order to replace it, the entire steering assembly has to be replaced. The switch is inexpensive, but the labor (at least at the dealer) is not. There may be a cruise control specialty shop that could do the work for less, but I've never looked into it because there are few opportunities to use cruise control on California freeways!! (I don't mean that it's stop and go, but you have to change speeds, accelerate and/or slow down, rather than cruise along at the same speed).
I only put about 900 miles a month on the car. It is garaged, and we don't have salt or sand winter issues here, only rain. I have two music rehearsals a week at a venue 25 miles away, and that accounts for 400 of the 900 monthly miles; with the music activity, I would likely rack up only 500/month, since the office is only two freeway exits from the house.
