HI Shanks, I certainly don't really need to reply here, because "wilwren" has done his usual excellent job with excellent material for you.
Just two things: From my personal experience on three "dexcool victims" of my own, and reviewing those lower intake gasket pictures, that is exactly the mess I found mine in too. (for a minute, I though someone had borrowed my pictures,,,)
Secondly, I have converted all of my (and family members) GM vehicles (including my 2002 GMC 5.3L V-
over to the "all compatible, mixed with any color" coolant by Prestone. It looks WAAAAAAAAAAAAAAYYYYYYYY better to me than that "pink poison."
(With appologies to the death-cool manufacturer, as I'm sure if they could "turn back the clock" they would have done things a lot differently.)
Oh, yes, sorry, one more thing: (yeah I know, that makes three things): I have had great success in disconnecting the lower radiator hose to drain.
Good Luck. You have received good advice.