A good friend of mine, Bruce Howlett, kept a journal while building a guitar from a kit that is a worthwhile read for anyone thinking of following suit. You can read about the adventure, misadventure and the great reward of the fruits of such efforts here.
Is it ok to tune your guitar while it has a capo on? Could it hurt the strings? Guitar? Capo?
I have played guitar and used capos for more years than I want to mention, and I have never hurt the strings or the guitar by tuning (or more accurately, fine-tuning) the guitar with a capo on...nor have I heard of damage from anyone else.