I agree with checking the gas cap, twist it off and then back on. It has happened to me several times.
Are you going to the dealer or an independant shop? Either way, get another opinion. Also ask the genius that told you $8,000 to spell out what the problems are. Come back and post them.
Good luck!
Not all dealers and mechanics treat us like we're stupid. You just need to sound like you know what you're talking
about and find a dealer or independent you can trust.