How long have you owned it? If it is a while, then you know the service history of it. Buying a different used car is always a cr@p shoot.
Personally, if I liked the car and it ran well and it's been maintained, I'd keep it. Do at least part of the work if you can. It will save you a lot of money.
I have a 08 Civic with 170k miles on it. Every time I think about maybe getting something else, I look at the road rash it has from a 100 mile round trip commute on major highways with trucks and ask why I'd spend new car money and subject it to the same thing.
Unfortunately, when they get old, almost any repair is at least 50% the value of the car. You can't think that way. Rather, ask how much you're saving over a new car. If it requires more and more repairs think of getting rid of it then.
Good luck with your decision!