I had a Maxxfan installed in the bunkhouse. You can install a power fan in any standard 14" x 14" opening where an existing vent is located. I have a second Maxxfan I plan to install myself in the bedroom. It is quite simple. Just be sure to use the correct sealant on the rubber roof. Follow this link :
for a video showing just how easy it is. While the video is Maxxfan specific the basics are the same for all vent fans. I had thought running 12 volt power to the fan would be difficult but it is not.
The Maxxfan I purchased (same one as in the video) has a remote control and can also be set to work automatically via the built in thermostat. It can also be used as a ceiling fan with the lid closed, a Maxxfan exclusive.