Gary,
I feel for the predicament you are in and wish there was a way to get you some help. I would hate for you to order an expensive inverter if the one you have is working O.K. and it is just a fuse or something else that can be fixed easily. If the current charger inverter is bad then the Magnum 2812 is an excellent choice for a replacement. There are no major wiring changes given the AC wiring you have now to the current inverter charger is what you would use for the Magnum. Also the DC wiring, just two large cables from the house bank are all that is needed. The temperature sensor is a different one and that would have to be run to the house battery bank. The existing phone cable I think would work for the new readout control panel. All in all not too much effort is needed to change this out. This is plug in play in a sense, but there are set up menus to go through and I am not sure about the transfer switch, seems that is some kind of internal plug in module that is an option on this charger. Maybe a Magnum owner can chime in on that subject.
It looks like you are on the Oregon Coast from your posting. Where exactly? Maybe there is another Beaver owner out that way that could help you trouble shoot this. Richard Tracy had a mobile service guy come to his RV in Newport and he trouble shot his leveling pump that had a bad solenoid. He seemed to be pretty happy with this person and maybe could pass along the name if you are near the Newport area. I called him to try and get the name but he was not answering at the moment so I left a message. I think some help is in order if we can stir some up...
Later Ed