I've never done one on a barn dor Burb,but my G-10 van's rear door glass was pretty easy,I just used a flat bar to gently pry the rubber away from the sheet metal--once I got one corner loose I was able to push the glass out,with the rubber still on the glass--I used a peice of insulated wire to draw the rubber back in when I installed the new glass,just like you would on a pickup's rear window..
Afraid of busting the glass?..what I did was "practice" at the junkyard FIRST,before I attempted to do my van!...the guy at the one I go too is pretty cool,he doesn't throw a tantrum if something like a rear glass breaks while your trying to get it out--heck,half the time his crew cant get one out on the first attempt either!..since they crush most everything older than 10 years now,they aren't too upset if a window gets busted,its only going to get smashed anyways,right?...