My Dometic RM 3663 goes directly to LP in AUTO mode and will not operate on shore power. The fuses are all ok. As I understand it, this is most likely a failure of the electric heating element. Questions: 1. Could this be something other than the 120 V heater ? 2. I'm pretty mechanical as old ladies go, but I'm still something of a nervous nelly. Is replacing the 120 heating element easy? 3. I can't find any local rv mechanics. If I'm not up to a DIY job, how do I find someone to do it for me? P.s. I've found the installation and user manual but can't find a technical manual.