RV Repair: RV Ceiling repair, class a motorhome, electrical wires

I have a 1984 Fleetwood Chev P30 Class A motorhome with ridged foam celing covered in some type of vinal wall paper. In the bathroom/shower area a lot of the ceiling is disentegrating so I need to replace it. Any ideas on how to do this?

If you have done this type of work before it wont be too diffulcult, but if this is your first attempt then you will need to go very easy. I searched for a diagram of your ceiling material but had no luck. The ceilings are sometimes a single sheet or a module, either way you need to remove the cover and see. Once you determine this you can remove it in pieces either way. When you replace it you can do it as a module. Most of these wil have channels in the foam at the top for electrical wires. If you could send a couple of pictures I could most likely match it to information I have.