diagnostic code reading

[switchex]

Hi.. my father in-law has recently purchased a 2000 Sonata with about 30K on it .. yesterday, the check engine light came on and he reported that while drving the engine was acting up, riding a bit rough or shaky .. however, both the light and engine problems went away after a few months .. my question is:

How can I ready the codes in the Sonata? I new how to do this manually without the use of a computer on my old car .. Can the same be done on this car by connecting the 2 wires (usually under the dash) together and read the number of blinks on the engine light?

If not, what is a good diagnostic computer to buy?

Where can I find a list of code and their meaning.

Thanks.