If you are unsure the last time the oil was changed and it looks remotely dirty, just change the oil. It takes maybe 20 minutes, would run you maybe 25 dollars with your filter included, and is substantial to the life of your motor. I believe you would want to run a 5W30 Castrol oil or 10W30 if you have high miles on the car. At most auto part stores they have a book that will tell you what oil filter your car needs. As far as the ABS light, don't take out the bulb (bad advise). Check the ABS sensors to make sure they are plugged in and not sheared by the wheels. If someone didn't have an ABS tool to replace brakes they might not have pushed the caliper all the way back in and that can sometimes make the ABS light turn on. Also check to make sure you have plenty of brake fluid and that the master cylinder is not leaking. My ABS light came on right before the master cylinder went out and my brakes went out the next day. Replaced the master cylinder, ran new brake lines, and now no ABS light.