changing gearbox 94 Sierra

I've got some "play" in my steering, had it checked at two places. Both said stearing gear was worn (108K mi.) Got a quote from GM dealer today, $750.00. Sounds steep considering box sells for $180.00. Thought I'd try it myself if I could get some "how tos" or maybe a site that could take me through it step by step. "94 GMC Sierra 1500 4x4 w/power steering. Thanks to all that help.