head gasket replacement is it better to rip out the engine and do it or just take the manifolds off and do it that way??

both i am using almost a whole resevoir full every day, but granted i am running 80 mph down the freeway at 3k rpms but thanks for the advice i need to get the insurance on my other car before i start tearing into this one. and hey how about a front motor mount are they hard to change with the engine in the car, mines completeley shot

thanks that will make this go alor smoother!