My '92 Limited has a rear A/C on a separate 20 amp service. It goes to a dedicated 20 amp breaker box and the box is mounted in the overhead cabinet above the bed on the oposite side of the main breaker box. Can't help on the routing of the drain hose. I bought the trailer used. It was a custom build for the original owner and I assume the A/C was installed at the time it was built.
I'm having a condensation pan problem with mine. Somebody really screwed up the pan and it leaks when I use the rear A/C in humid conditions. I tried to repair it several years ago and I'm sure the drain hose goes through the street-side wall. Three years ago I decided to have the local Airstream service department install a new pan. When I went back for the trailer I was told they couldn't remove the A/C since someone had used Vulcum to install it and if they removed it they might damage the A/C so much that it would be ruined. I don't know enough about Vulcum to know whether or not this is logical so I paid the $175.00 for their charges and have lived with it. I have a friend whom I've met since the above experience. He's a service manager for another company and has offered to tackle it when the busy season is over. He says it he won't trust his mechanics on Airstreams but that he will personally try to cure my problem for me.
'92 Limited 34ft (now sold); '96 Dodge Cummins 4X2, 5speed