M50 has a timing chain and requires no valve adjustments.

Check for shaking at 55-60 mph, overheating, check that the windows, A/c and power seats work, and check the tranmission. It should shift smoothly, and go into gear as soon as you move the shift lever ... if there is hesitation, it might have a problem (this if it's automatic). Other than that, there isn't much to look for.