bigtime trouble-1990 lumina apv

my uncle got this van from a friend for 500 bucks, kept it for about 3 months, then gave it to my brother for free. It ran really shaky after about 45 mph. Then after about a month it started messing up and not starting half the time. Then it got to where it wont start at all so we replaced the battery and had the alternator checked (it turned out fine). So we put everything back on and it started once so my brother backed it up the hill and when we did a lot of white smoke came out of the tailpipe. So we checked the oil and sure enough there was water in the oil. What can I do?????????

Pull it apart, see where the leak is.

Ive started pulling the engine apart but ive run into a minor problem. My brother filled it with gas right bofore it stopped running so now im having to try to drain it but my syphon isn't long enough.