sohc help

yes i do own a 97 base sohc. on top of it, the car is an automatic. it has good mileage on it, 88,000. i was wondering what kind of mods i can do to this car and how much hp the car will be able to hold. i already hav a fipk by k&n. i was thinkin bout a set of shorty headers from 3kgtmotorsports, as well as a downpipe. if i hav any money left i was considering custom cat-back exhaust. i have about 800 to work wit. anybody hav any ideas. also i was wondering if they sell shift kits for this car?