I helped another Supra owner go from the stock springs to a new set of Eibachs on all four corners. The fronts were definitely harder, but once we figured out one side, the other wasn't too bad. During the whole process, I broke two cheap ratchet wrenches... I had to run to Sears to buy a good 24" breaker to get some of the bolts loose. Follow the factory manuals and it's a doable process, though not for a beginner. It took the two of us 6 hours (including several trips to the hardware store).
We didn't need to use a spring compresser. I weigh 180lbs, and it was just enough to get the retainers back on with the shorter springs.