Do the repairs yourself.

You would be suprized at how easy many repairs are. The problem is the time and mess that body work brings to the table.

If you don't want the mess then strip everything off the car you can to save money at the body shop.

I would say if your not looking to sell it then any amount of money would be fine. The amount of money you put into a car is only important in three situations.

1. If you are trying to make money off it by selling it later.

2. You only have a limited budget to work with.

3. How important the car is to you.

If you are planning on keeping it then #1 and probably #3 are irrelevant because the car is important enough to you that you won't sell it.