I'm helping a friend with a 2005 clutch install this weekend. He has a stock clutch in it currently and is moving to a Spec Clutch. How many hours will this install take? I can only be there for Saturday, is this something that can be done in one day?

Looks like a lot of work to me, although I have not done it. Answering 2 questions might get you a better response from those that know:
Will you have the car on a lift or jackstands?
How experienced are you?

*I* can't do it in a weekend... But if you are a very skilled mechanic in a well equipped garage it is definitely feasible. Both times I had a shop do it for me it took 2 days and about a thousand dollars in labor... It is not trivial.