RV Repair: RV Microwave Oven, ge microwave oven, magic chef

Question
I just purchased a GE microwave oven to replace the old Magic-Chef in my RV. The size was right as was the price. When I got it home, I discovered a warning on the back that said "NOT FOR BUILT-IN INSTALLATION". The only difference I can see is that there is a cover over the exhaust in the rear of the old microwave. It will fit over the exhaust on the new oven with minor monifications to the cover. Am I about to burn the place down?

Answer
Microwaves are microwaves, of course, the only difference in the "RV" microwaves, is that they come with specific fresh air intake and exhaust deflectors so that the microwave does not over heat while in use.  Check the one you took out, top, bottom, rear, you should see pre-bent shields/ deflectors that re-direct air flow.

Garry