the passenger side one is not too difficult to replace, but in order to get to the driver's side one without losing your sanity, the steering rack has to come out first (fairly easy to do).
I'd recommend using a engine hoist (cherry picker, a-frame, etc) to lift the engine slightly after the mounts are loose.
That said, I replaced my passenger side mount by jacking the car up, and stacking 12 inch wide boards under the engine, then let the car down just enough to get the old mount out, and the new on in. Jacked the car back up, tightened the bolts and removed the wood. Be careful about denting the oilpan though... spread the load out. I had towels placed strategically to cushion the load a bit, but still dented the pan a bit.