Hi Crutch,
If your Wilderness has 50 amp electric service, and is prepped for an optional 2nd A/C unit, it should probably cost around $1,000, maybe a bit less or a bit more.
If you have only 30 amp electric service, you'd have to first upgrade the electric all the way from power cord through internal wiring, and replace the main circuit breaker panel. That would add a lot of cost.
And if the design of the trailer didn't include an optional 2nd A/C unit, that would increase the difficulty and cost of the installation.
You might take a look at portable floor A/C units that exhaust through a window. Even if your trailer has only 30 amp electric, you could probably run a suitable extension cord out to the 20 amp receptacle on the power pedestal to power the portable unit. While they take up floor space, I think they cost $400-600. Look at Home Depot, Lowes, or Amazon.com.