Layout,
This system is modeled after another system and it is a bit different than what people think. The layout is used in emergency systems where the need for high voltage is not critical. It is simpler than the generator type apu because of a number of things - parts are cheaper and it is easier to maintain.
The inverter from what I saw was not inside the APU but mounted in the sleeper and a shore power hookup was provided. I don't remember which one it was, don't have my notes on it here but I do remember that it was a sturdy one.
The APU provides 12 volts to the inverter by using a 200 amp alternator (I think that one uses a Delco si type like your truck) and it does work well without the maintenance issue as you have with the generator - alternators seem to last a lot longer. The A/C uses some off the shelf components (Sanden compressor was the one I saw) and is serviceable by any competent A/C mechanic - if I remember right, it is a orifice tube type a/c unit. I don't know where they get 33k BTU, I am thinking it is about 21-25k BTU from the size of the compressor.
I don't know what engine you have in yours (and my offer is still standing for a few hundred for it even if it is leaking like a sieve) but the Yamar engine can be a PIA to repair and is a bit different than say a Kubota or Cat, on both parts and servicing.
The controls are digital by the way, they claim analog but that's not completely true. The battery level triggers are digital and I think the safety shut down system is too.
Would I buy it?
I most likely would IF I would get a component manual and diagrams for the electrical system with it as part of the deal so I can or my mechanic can repair it.