Depends where the plug is on the block - I seem to remember the V6's being not that far down, but I could be wrong there (its been a few years now since I had a gasser) - regardless though, just open the drain cock on the rad, recover the coolant into a rubbermaid container, r&r your freeze plug/blcok heater, "reinstall" <img src="/forums/images/graemlins/wink.gif" alt="" /> coolant.

But have a look at your frost plug first: assess its accessibility (<img src="/forums/images/graemlins/cyclops.gif" alt="" /> heheh - are you confused?) AND make sure you do the right one - fp block heaters want you to use a specific freeze plug, and install the element in a specific position (mine had to be at 9:00, but it varies)... you probably know this already, though.