Intake Manifold gasket Leak

I recently took my 1998 Nissan Altima to get a diagnostic on why it idles rough or pulses, it came out that I have an intake manifold gasket leak and some vaccume line leaks going to the intake manifold. question: Is it possible to seal an intake manifold leak from the outside, as my repair book tells me it's nearly impossible to remove the intake manifold to get at the manifold gasket without removing the engine head because of tight spaces and hidden bolts facing the fire wall. I do most car repairs, but this may be to much for me, but if it's possible I'll try to tackle it.