is it worth it to put new heads on a motor with 145,000 miles on it

I had pressure test done on the head gaskets for my Cadillac Catera. The mechanic said that the heads were bad. Is it ok to just have them replaced or should I just get a new engine, the mechanic recommended a new engine? Most of mechanics I talked to said to just replace the engine because the heads won't sit right if replaced. I'm wondering if they gave this recommendation just because it'd be easier than replacing the head gaskets.