Throttle problem in VW passat

I have a '98 VW Passat that I love. It has about 140,000 miles and I commute about 250 miles/week. It has entered the golden years, but I can neither bear nor afford to part from it, but there’s always something. The latest-- the engine check light went on and indicated a throttle problem. Our local independent VW-ish emechanic said the idle throttle switch needs to be replaced, but that it wouldn’t be dangerous to drive. Some days it drives fine, and others the throttle thrums up and down at every stoplight, and there is a high idle all the time-- then it stops. It is an expensive repair. How do you know when it’s time to get a new car? I really really love Greenie, but she has always been a bit prone to the unexpected. Still drives beautifully (most of the time), body, interior, engine, clutch, etc. in great shape, but one window switch doesn’t work, sunroof doesn’t work, locking system is interesting, etc. I don’t care about any of that stuff, but I do need to get from here to there safely. Thanks!

I doubt if it is time for a new car. How much is the extimated cost for the repair? Now how many months of new car payments would that require. You car should have another 100,000 good miles on it.

What was the error code? That would help us understand what is going on. My guess is it is the throttle possition sensor that tells the car’s computer how far you are pushing the throttle. I can’t remember, but maybe it could just be cleaned in possition.