I'm planning on unstepping my mast for maintenance purposes in the next couple of weeks; I'll be using plans found at the catalina27.org FTP archives for constructing and using an A-frame. I priced out the materials the other day -- should be less than $50 and as mentioned above, I'll do all my own stepping and unstepping in the future.
I haven't done the job before but with a couple of able seamen it should be fairly straightforward.
Here's a link to A-frame instructions
. They make assumptions about the sort of rigging you've got and of course dimensions, so you may need to make some modifications. I plan to construct mine out of smaller pieces since I have storage issues; I also plan to add some purchase to the lifting system. I think my mast is about 75 lbs.
Here's a link to a YouTube video
in which some folks follow the instructions above. They also made some modifications. I'll basically be following the procedure they used.
Good luck; let us know how it goes!