Back home, I tackled the subframe bushings today with 100% success. All it took was a Sawzall to cut the sleeve, and the rest was a piece of cake. Each bushing (from core removal to outer sleeve removal) probably took me 20 minutes or less after I mastered the technique.
I also removed the remnants of the paper gasket on the back of the differential, and sealed it back together. I installed the differential with the polyurethane bushings, and torqued the rest of the bolts I had removed during the process accordingly. Tomorrow is simply reassembly, along with fabricating MDF mounts in the rear for the speakers that arrived while I was on vacation. My sub box from Chris is set to arrive via UPS on the 11th, so once I have that put together, I'm taking the Z in to have the audio professionally tuned (between the sub amp, speaker amp, and headunit).
It couldn't be a progress post without a picture, so here's the subframe back together, its last night on the garage floor:
