I added a comment to your pics. If you feel the buildings are structurally sound, it looks like you don't need to do a lot but clean out the mess and buy a feeder and waterer. I prefer the plastic ones, white with red, which are not paraticularly expensive. You might want to paint the inside of those nest boxes with a gloss paint just to make cleaning easier later on. I wouldn't paint the roost, if that is what that is; I'd scrub it with an ammonia solution and then a bleach solution, then I'd oil it with vegetable oil. I wouldn't use the wooden feeder, if that is what it is, because you can't really clean it. I'd probably remove it, or maybe turn it into a second roost somehow, perhaps a lower one. It looks like they used a wider board for a roost, again if that is what it is, which is a good idea as it is more comfortable for them than a narrow board or something like a broomstick.
Basically I'd say you have a very old fashioned chicken coop, which is a rather wonderful thing to have!