Can someone advise me on the purchase of an automobile please?

I am looking to buy a van from a private owner. It is a 1995 Chevy Lumina ATV minivan. It is 1,000 which is all I can afford. It has remote sliding door, fold down removable seats, power seats, windows and door locks, ice cold front and rear air, cd stereo system. Everything worked inside such as lights, signals, wipers, etc. The body is devent only some scratches but no body damage, no rust. I drove it and it seemed to run good. There were 2 lights that remained lit on the dash. One said service traction control, the other said service anti lock. The guy said one tire in the back is slightly smaller than the others which is why the service traction control light remains on. He also said that there is a slight oil leak but nothing major. When I first backed up to test drive it it did shake a little but didn't shake any more once I got going. Seemed to shift ok. Looked under hood at engine and it did not vibrate or anything. Please give me some needed advice. I am supposed to meet him in an hour to purchase the van but need to make sure I am making the right decision before I agree to get it from him. Help!