Here is a tip to do it yourself, I know it sounds odd but it works really really well:
Take a tube of toothpaste and put a big glob on the disc, smear it around the whole disc with a cloth, then wipe it all off. Disc will work like new for some reason.
I have done it many times, to CDs and DVDs that won't read anymore because they are so scratched, but they work fine after you do this.