I think you'll be fine replacing 1 stock gasket as long as you don't have a hopped up motor. If the compression ratio has changed, you may have to use something other than stock though. You can probably get the gasket through a dealer unless you want the whole set, then I'ld go dennis kirk or shade tree. The dealer is nice because they will give you a tourqe spec if you don't have a manual.
You don't have to believe everything you think!