Do you reprogram a used computer? on 2004 Kia Optima

Does a2004 kia optima lx computer need to be reprogramed if you buy it used from a wrecking yard?

Asked by for the 2004 Kia Optima
You can't really 'reprogram' a cars' computer- but you can 'reflash' it. But thats a last resort if there are problems with the ECM.
How can I find out if there are any problems with the ECM on my own?