Where did you get the oil changed? I bet the oil light staying on is a result of a cheap oil filter.

Are all of the headlight, parking, and tail lights coming on? If no, replace bad bulbs. If all of the bulbs are good, check the grounds (or have a shop check them) in the trunk and engine compartment for the light assemblies. Are both headlamp bulbs the same age and make? Sometimes slight differences can upset the balance in the bulb failure sensor. If all of the above checks out, replace the sensor (a used one is cheap!).

For the Check Engine Light, check the 700/900 FAQ to get the "on board diagnostic" (OBD) codes. Real easy to do yourself.

-Ryan
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Athens, Ohio
1987 245 DL 314k, Dog-mobile
1990 245 DL 134k M47, E-codes, GT Sway Bars, GT Braces, Draco Wheels
1991 745 GL 300k, Regina, 23/21mm Turbo Sway Bars