If you want to make a complete copy of the disc, the simple fact is that you cant. It will be copy protected. Should your disc become damaged, and you have registered the game with the Software Vendor, then they should send you a replacement, free of charge.
If you could copy it (and yes, I know there are Way's around copyright protection systems) you would need a dual layer capable drive, and blank dual layer DVD to do it.
Many brands around, but your drive must be DL capable, and the disk's are a lot more expensive than the standard 4.7 variety.