The above threads are what most of us here used to successfully change our bushings. Splurge at GM and buy the new bolts while you're at it as it make re-assembly much easier if, like mine were, your oem bolts are rusty. You will have to get the back end up higher than you think in order to install the GNX bushings so be certain that #2 & #3 are loosened enough to allow for 'travel' up. The site gives you a guide as to how not to get the body on cock-eyed.
Straight fwd mission, just a little time consuming...and could be tough on the beer supply
HTH
Jim