The KBB value of the car is is not relevant to your decision.

If you need the car, fix it.

If you don't need it, and can afford a new car, then don't fix it.

If you really want to know what your car is worth, take it to Carmax and have them make you an offer, or call some dealerships and have them tell you how much they will give you on a trade. Then check Craigslist for cars similar to yours to see how valuable they are are in your area. You can even post your car, and see if anyone makes an offer. That will give you a ballpark for the value.

Take that number and subtract the cost of the repairs. That will give you the car's actual "value" to you now. So see if you can get a better car for that much.

So say someone offers you $4k for your car, but you need to put $1k into it before you can sell it or use it. That makes it worth about $3k. Can you buy another car for $3k, plus tax, plus fees, that is better than yours?

Remember, you've already paid the taxes and fees on this car. If you switch cars now, you'll have to pay that money all over again, so add that to your calculations.