Oil leak?

I've been driving my sister's 97 sentra because the clutch on my civic is acting up and i'm fixing it. So I'm trying to get the part and I decide to get gas for the sentra and when I start up the engine, it won't start. i tried it again and it came on, but the oil light and the check engine light both came on and the car died again when I tried to put it in gear. Bone dry. I bought some motor oil and put in two quarts, and tried unsuccesfully for 15-20 minutes to get the car to move when I put it in gear. The engine was vibrating a lot, but after a while it didn't die when I put it in gear and I actually managed to drive it all the way home and it didn't give me any problems. I checked it again after I got back and it was running like normal and the check engine light is still on. Now I'm trying to figure out if the check engine light is on because of the oil leak or if something in the engine is damaged from the lack of oil. Any help at all on any of this would be great. Money is tight, so I'm trying to do as much of this myself as possible.