What is a broad figure of buying and getting an ac installed on an 8ft shortwall with bracing and electrical in place? Trying to decide if getting it done at the factory for $3,000 is over priced.I will be calling the  RV place 20 miles from here on Monday for a price also.

Other thought is to use a standing air conditioner.

With the bracing installed and the electrical already in place, THREE THOUSAND DOLLARS is a rediculous price to pay to have an AC unit installed !!!!!!!!!!

The units for your trailer would be in the 13,5000 BTU range, which are currently selling for ~$750 and up. You will need shrouds and extras which will add a couple hundred to that figure. It can be done for ~$1000 depending on the brand and model.

The units come with very good instructions and can be a one hour DIY project, for anyone with a basic understanding and ownership of simple tools; socket set, screw drivers,  etc. Basically the installation consists of four bolts, a weather seal and an electrical plug. A  shroud and garnish finishes it off.

The hardest part is getting it onto the roof, two people or a tractor's front loader works quite well. (aprox 100 lbs). Putting a piece of plywood on the roof before hand, and setting the unit on that, helps a great deal.

Here are some choices:

http://www.campingworld.com/category/air-conditioners/370