yes, the disk's content is stored in the film (side which has the game artwork on it) so as long as the scratch is in the shiny side it should be repairable. i had san andreas done a few years back for £2.50 and when it was returned it was like new (it didnt even work when i handed it to them)
all lot of second hand game shops can do this as they get sold a lot of games that arent in salable condition, i think cash converters resurface disks too. at least i know the one near me does