Replacing the original fan seems easy enough, and it would perhaps be the easiest installation in the whole house. I've put two fans in elsewhere, and they were trouble for different reasons. This is an existing fixture that's right in the beam. My real concern is what I'd have to do to extend cable if I must.
I don't see how the original fan was wired. There's no crawl space in that part of the ceiling. From what I can tell, it's just inches away from the roof itself. The beam was painted by the previous owners, and it hides anything that might have been done. I don't see a painted over wire running along the beam, so it must have gotten its power somehow.
Does anybody have an idea of how a fan like that is wired? Is it practical to DIY install the second fan? The worst installation was changing a light fixture to mount a fan. I had to put in a new hole two feet away from the original fixture and run wire to it. I put the radio receiver for it in the original fixture's hole. Am I looking at something much more complicated?