88 pontiac sunbird update

Well I finally got my sunbird to run after finding a good mechanic. The Temp. Sensor was out and reading -38 below and the OT sensor was out. I also had the Cat. Convertor replaced. Total cost was about $650. I am just glad to have it running. My gas milage is about 25 per gallon which is a little less than it used to be, I was told that happens with age. The car has 196,000 on it. The car has always bogged down, lose power when you go uphill. Is this normal for a 2L? or is their something I can do about this? My car needs a paint job the sunroof and trunk leak, the dash plate and middle console are cracked and the material inside could be replaced. I do not know if I should fix-it up(It's kinda neat they are not very common) or just let it go and drive it till it dies. This is the only car I own.

Thanks
bjj