Hi, George. Nothing special is required to put latex paint over oil based. What is necessary is the same prep work you should do for all painting. Wash the walls and ceiling with tri-sodium phosphate(TSP)and rinse, then fill any holes and so on with spackle and sand. Then put on a coat of primer/stain killer.
A good tip is simply to buy the best paint that you can find. This is available at the specialty paint stores rather than the "big boxes". When you calculate the cost of 5 or 10 bucks more a gallon over the more years of use and ease of application, spending $25 or so a gallon makes sense. If you have ever done tough painting like cutting in wood window frames with really good paint, you appreciate the difference. Also, you might be able to get by with fewer coats of good paint where you would have to apply more coats of cheap paint for the same coverage.