Want a cool trick? It's not considered safe, but hey, you trust a GM product anyways right? j/k

As you may have already realized the rear shock mounts are hidden by the back seat. After you get access, use an air gun and zap the center nuts off, leave the mount in place. This must be done on both sides at same time to allow enough travel. Now jack the rear of the car up until the springs max out an relieve the pressure. These aren't really long nor really tight springs, and they are in an area where they won't just fly out of the car. After the springs relax then remove the lower nut/bolt that attaches them to axle. Now remove the mounts. Reassemble outside the car with a compressor and reinstall as a unit.
I can put them back together myself without a compressor but it's far less safe than the disassrmbly.