existing paint is white oil-based high gloss.

sand it well, then repaint with oil-based primer and your paint of choice.

I can't speak to the quality of the paint used but I can tell you that most all paint formulators are making a latex paint that will work just fin over any oil so ling as the oil was well cured. Of course if it's K-Mart brand paint there's no telling what was in the can.

As an aside Benjamin Moore (the only paint worth buying) sells an alkyd oil primer over which they recommend you apply their 100% acrylics (code speak for latex) paint.

I had a similar circumstance, except the oil paint underneath was dry for a few years. At the suggestion of an older fellow who has many years flipping houses, I used lacquer thinner. He said he discovered this by accident.

I soaked a rag in lacquer thinner, squeezed it out then washed the the latex off. The lacquer thinner dissolved the latex, washed most of it off and what was left was set into a thin layer of the oil paint base that the lacquer thinner had dissolved. I let it dry for an after noon then could repaint or touch up with oil as normal.

Just be aware of how the thinner is interacting with the oils. I've been able to save a lot of time and money using lacquer thinner.

i'm going to prime and paint over it. I hope its ok.