Dan,
I just did this on slingshot. I ordered the Sheaves from this guy:
http://zephyrwerks.com/ for slightly less than rig-rite charges. The customer service is way better. Once I got the mast down, I found that one of the sheave had already been replaced with a larger than expected pin. I sent the sheave back to him, and he adjusted it free of charge.
I dropped the mast in the marina, using one of the cranes that they use to lower melges's and what not into the water. It was surprising easy.
