The home was originally constructed in 1955. Since I have no way of knowing when the original paint job was done on this bathroom, I cannot easily determine if the old oil-based paint contains lead or not. So what do you suggest when my goal is to remove the peeling latex as well as to prep the underlying oil-based painted surface for either latex or acrylic when there is a chance the old surface might contain lead? I want the safest and best method possible that I can do myself. without having to call in a Hazmat team.
You should be able to test the paint for lead content using one of the lead-test kits you can pick up at Home Depot or Walmart. Especially if the oil-based sub-layer is exposed in places. If the first test proves negative it's worth scuffing the paint with some sandpaper and testing again, just to be sure.
If it's lead-free you're home free.
Depending on where you live, and how much area you are doing, there are homeowner lead-paint removal classes that show you how to do the job safely. Not all cities allow this however.