RV Repair: re-sealing roof on 5th wheel, 5th wheel, fiberglass roof

Question
I have a 40' Travel Supreme which I have added sealing compound to the roof each Summer for 3yrs now.  

Feel like I probably need to take it down and re-seal as the caulking is getting pretty thick.  NO LEAKS.. just maintenance as I live in it full time working coast to coast.

Do I just scrape the old off and apply the new, or can I use a sander?  After removal of old sealant...do I need to
prep prior to re-sealing?  With what?

Was going to have this done by an RV Doc...but he wanted $750 to do this and I felt I could probably handle it for a lot cheaper.

Thanks.

Answer
I'm assuming that you have a rubber roof. If so, you should be able to scrape it if you are very careful. Sanding would be OK, but you still need to be very careful. The only prep you need to do it make sure it is completely clean. Soap and water would be fine. If it is a fiberglass roof, follow the same steps, but you don't have to be quite as careful.