Depends on the shop. Some will ask you how much you want out of it, others will immediately throw it onto GunBroker with a starting bid of $.01 and no reserve, and move it within a week or two. Retailers don't want product to sit, it needs to turn over and make money. This is why you need to call around and ask about policies.
If you want it to just be held then ask how much for gunsmithing/cleaning + storage fees while you deal with the legal issues. If you get convicted the shop can still consign it afterward.

