The trouble is finding the transformers anymore. There's some FET boards and control boards out there for them yet. But if you melted a transformer, short of rewinding it, it's dead.
The MC2 is the same as the SW except for no grid sell-back capability and one other difference I can't remember. It will probably cost more to get it fixed than you can buy a used inverter for. I just sent a SW Plus 5548 to North Carolina a couple weeks ago, and I had two SW Plus 4024's, and before that a SW4024. I think the dealer still has our SW4024 in his warehouse and I'll bet he'd sell it for $1,500.
Like I said, with the new one make sure you hook the shore power to the AC input instead of switching the output. Use the internal 60 amp pass-thru so the inverter can sync with it. Those inverters do not like having the output switched, even with a transfer switch or interlocked breaker set. You'll blow another transformer when it makes the big "thud" from hitting an inductive load out-of-phase on a transfer.
--
Chris