If all you have is a 30 amp plug, you are going to bite off more than you can chew by trying to add an AC. One part is the wiring, all the way back to the breaker panel for the AC. Next is rewire the 30 amp from the outside connection, to the breaker panel, with 50 amp service. Then you will also have to change your converter and breaker panel.
As for the vent, you can pull the inside cover and see if the vent is boxed in. If it is, it should hold the AC. If not, will need to remove the ceiling, and box in the vent opening. Sounds a like a lot of work, and $$$$, and probably is, to both.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT