Take a look at the pictures in the string from just-n-time
Search on author and look at vacuum leak. It started last spring I think, but he took pictures of where the dealer is going for $2000.

Pointing to the intake gasket says they troubleshot to a vacuum leak did you ask them to show you the problem and how they got to the intake gaskets.

Guides? there are valve guides but you have to take the heads off to replace them and symtoms not just rough idle. Anyone know of other guides they could be pointing to?

For $2000 they should be more than willing to explain how they know thats it and not something else.

Tell us what your symptoms are and what the shop said in detail.