To me, the hardest part is plucking. We went ahead and got a WhizBang kit because we do a batch of meaties every year. However, for older birds like you are talking about, I would just skin them. I'd also stew or can them because with old birds the meat is pretty tough. I like to can it because it's ready to toss in a casserole like chicken enchiladas, or chicken soup that way without having to defrost. Lots of info on doing your own processing online, its not hard.
I butchered my first rooster yesterday, and I found it very tricky and messy. Hardest part was removing the vent - YouTube videos made it look easy but my poor roo looked like it had been in a car crash by the time I'd finished. Hopefully I'll make a better job next time.