Drum to Disk? rear brake problems

Hey i was told today by firestone, they wont put the shoes on my rear drums because something was all fucked up and they didnt wannna do an unsafe repair. Anyways what all the repair entailed was pretty much replaceing the brakes and they wanted like 250$ for it. well im not to happy with that. so i was wondering. if i have to replace them could i just switch them out with a good aftermarket brand, or even a stock rear disc from one of the nicer eclipses? If so any ideas/tips/brands to watch for or keep in mind will help.

Drum to disk conversion..
http://www.2gnt.com/www/files/reardisk.htm