A parking brake rebuild kit is only about $25-35, it comes with shoes and springs, IIRC. I rebuilt my 123 chassis parking brake only to discover the star wheel adjuster had been put back together wrong by the po. I had the kit so I rebuilt it while it was apart and put in new shoes. You might want to pull the hubs and inspect before you order anything.
Then again, if you're asking how much this will cost if you take it to a shop, it will all depend on what kind of shop you try and how much integrity they have. Some are obviously better than others.