You don't need a code reader; in your car there are two black boxes mounted near the driver's side strut tower that you use to read codes. Full instructions are in the FAQ.

I would buy a multimeter (you don't need anything fancy) and check that the TPS, IAC valve, AMM, and ECT sensor for proper voltage/resistance (again, all in the FAQ). Re-aligning the TPS wouldn't be a bad idea, either, it's very easy once you have the throttle body off and they can shift out of alignment with time, esp. if the throttle body gets full of baked-on gunk.

Also check for spark; you may need a new rotor or cap, new plug wires, new plugs, or all of the above. If your fuel filter is old it might be causing restriction. Clean the IAC valve, and above all check for vacuum leaks, both with the engine cold and the engine hot to catch any leaks that only happen when the engine is hot or cold.

But don't be afraid of doing some electrical detective work, it's just a matter of touching wires to pins or sockets and reading the results on the multimeter. Kind of fun once you get into it. Try to do as much diagnostic work yourself before resorting to a mechanic if necessary, since it will save you big $$$ on labor costs. Good luck!

Jeff
1993 944T