Full coverage w/ state farm and gap insurance?

I just bought a CR-V. I have full coverage w/ State Farm. I bought Gap insurance for 287 at the dealership. I thought this was a good buy. My dad says that since I have full coverage if I have a total loss we're covered by State Farm for the full amt. I've had friends that have wrecked their cars and only... show more I just bought a CR-V. I have full coverage w/ State Farm. I bought Gap insurance for 287 at the dealership. I thought this was a good buy. My dad says that since I have full coverage if I have a total loss we're covered by State Farm for the full amt. I've had friends that have wrecked their cars and only got 3k back. Should I keep or cancel my gap?