There are no special tools needed, wrenches is about it but I am sure one of the DIY guys can talk to you about how tight 'tight' is and not to cross-thread, etc. Your LDS should be able to sale you a hose and attach it for a fair price and that is what I would suggest doing at this point.
As for length, I think it is about 24" but if you need an exact answer I will measure mine and post it when I get home.
Turning your head isn't a problem, it's just that you don't want to use this for an hour long site-seeing tour in the Keys because it would be uncomfortable. But remember, that isn't what it is for. If you have to switch to your AIR II the dive is over in all probability. Time to find your exit point and head up.
As for different lengths, don't think so unless you are going to use an LP hose and some sort of adapter but this is primarly an inflator hose. There is a narrow range in which it will work well.