Last winter I helped shorten and re-rig a Bristol 29.9 on Long Island, Bahamas (a scenic place to work on boats BTW) and working from
The Rigger's Apprentice, I can tell you that you can calculate your stay lengths just by knowing your mast length, however, I can't imagine anyone crazy enough to go aloft on an unsupported mast (even one stay missing). I've heard of yards that have a permanant mast crane that only charged $50 to pull the mast (assuming the owner is removing the turnbuckles and moving the mast. Or you could do what we did and
fabricate a hinge.
I imagine the cost of stepping/unstepping is somewhat dependant on what cranes are available, but keep in mind it is probably an hour long process for an experienced team of two folks so that's $80/hr x 2 x 2 (in + out) by my accounting, not counting the crane.