Does my 2010 gas tank have a rollover valve?

Hello,
I have a 2010 Prius and I can't put more than 0.2 gal into the tank at a time. I've taken it to the dealer and they've blown out the vent system. I took it to another mechanic and they tested out the vent system, charcoal canister, valves, etc. They say that the fuel tank has a bad rollover valve and needs to be replaced. They suggest a new tank (~$600 and labor ~$300.)
1. Does my 2010 prius have a rollover valve?
2. Is it an integral part of the fuel tank or can it be replaced separately from the rest of the tank?
Thanks.