Oil pressure

Unless the seller gave you a receipt for it's last oil change showing the mileage when it was changed, then you may want to get the oil changed now and start documenting the maintenance.

The oil change reminder is to be reset to 100% at each oil change. It will slowly go down depending on the type of driving you do. When it gets down around say 15% you should schedule your next oil change and make sure they reset the "reminder" back up to 100%, or the owners manual tells you how. If you have to drive beyond that point, it will not hurt anything, just take care of it next chance you get. Also, check your oil level with every gas fill up. This oil percentage has nothing to do with oil level like some people think.

If you don't know anything about the vehicles past maintenance, I'd change the oil and filter, now. Then you can start watching the mileage. Some vehicles have an oil service lamp that comes on when it's time to change oil and filter. Check your owners manual for info. If no owners manual, my.gm.com may have your owners manual. It's free to read online. With used vehicles that I don't know much about, I like to give it a tune-up, check everything I can.

I just had the same prob. it turns out to be the wiring harness that is right next to the engine oil filter. on mine it rubbed through the plastic harness but did not damage the wiring. I think due to the low voltage and it being right next to the engine block that is charged negative that it was interfering. I move the harness away about an inch so that it wont touch the metal and the oil light stopped coming on. problem fixed.