That is a tuneup a tune, in the car modification world, is a complete remapping of your cars ECU. There are several ways to go about doing this, the most popular being the AccessPort from CobbTuning.
Why do you say "apparently it's running rich"? What modifications are done to the vehicle?
If no modifications are present, you won't need a tune, and probably just need a good tuneup and maintenance check up. Sparkplugs, fuel filter, air filter, all fluids (oil, transmission and rear diff fluid, a radiator flush, etc...) are all things I would be doing right away. Do you have any maintenance records for that car? There may be a lot of other things that should be checked as well if you don't.