I wouldn't drill and tap a collectible gun, and I have actually refused to do it to Nazi and other collectibles customers have brought to me throught the years. I have done several Yugos for folks though. I charge $40, and that price includes the front and rear bases. Forging and polishing of the bolt handle runs $30. That should give you something to go by if you take that route.
BTW, the Yugo is an intermediate length 98 action, and requires the barrel face to be milled for the ectractor. It does not lend itself well to conversions to other calibers. If you ever decide to build up a custom gun, find a Czech VZ24. They are cheap and have little collector value, yet are made of high quality steel.
Balming