You paid $1,500 for the car and you're looking at $1,500 (possibly less) for the work. Even if you sold the car for $1,500, and put the $1,500 for the work towards a new car, you'd be looking at a $3,000 car. Any car you buy for that price is going to be just as likely to have the same problems, or worse.
If you get these problems fixed right, you'll know you won't have to deal with them again. Parts for GP's are pretty cheap, and if you're mechanically inclined at all the work's usually not too hard, so these are pretty cheap cars to keep running. I think you'd save money in the long run if you keep the GP and take care of it.
