98 Chevy Metro. pls help

I have a 98 chevy metro. I bought it about a year and a half ago and it has 160,000 miles on it. it has hesititated slightly since i bought it. mostly in 1st gear when accelerating. it has been getting worse. also, when puting the car into drive or reverse after first starting, it likes to die unless i press on the gas. the hesitating is getting worse and worse. Then the car stopped starting at all. i replaced the starter and that fixed that problem. Still has the old problems though. I replaced air filter, oil filter, spark plugs, spark plug wires, oil change, and still having the same problems. i just cant put my finger on it. ive been thinking it has something to do with the ignition, I.E., the spark plugs, wires, or coils. I have yet to replace the coils because they are rather expensive and dont want to be out that money if it continues. Today i started wondering about the transmission. It appears to have a small slow leak in T fluid. If anyone has any ideas as to what this could be, i would appreciate it. also, i had a salesman try and tell me that around 150,000 miles, metros 3rd cylinder goes bad. I think he was just trying to sell me a car. but the hesitation gets worse as the car heats up. Again, any help is greatly appreciated! thanks guys

3-cylinder or 4-cylinder engine? Assume manual transmission? Is your check engine light on? Have you connected a scanner to the OBD-II port? Any codes?

Its a 4 cyl. Automatic. Check engine light is on. Don't know the code but it deals with the air intake temperature sensor. Any ideas?

There's 3 trouble codes related to Air Temp Sensor - one for Air Temp sensor performance, one for high voltage condition and a one for low voltage condition. Need to know which one. Also need to know if there are any other P-codes (trouble codes) stored in the PCM. A problem with the air temp sensor circuit could explain the problems you've been having. You might just have some dirt in an electrical connector - can spray out with solvent.

Have you replaced the air filter?

^ I agree! The Intake Air Temp sensor will make the car have the issues you are complaining about.