How long does it take for a iphone to restore?

Ok so i jailbroke my iphone 4 a couple of weeks ago and it was coo n all. But i heard of the consequences or whatever and i was freaking tf out man. So i tried restoring it on my own but "Error" kept popping up, then i decided to go to this store by my school which basically repairs all types of stuff, i told them my problem and left my phone there but they said it might crash! Wtf so how long does it take for a restore?

About 20 minutes

It doesn't take long you honestly didn't have to take it to the shop all you had to do was put it in dfu mode then plug it in to the computer then it will say unknown device restore it. And what consequences for jail breaking? Do you not know that jail breaking is legal something's on Cydia are illegal but it's almost impossible for you to get caught.
Hope I helped