For the differential mount, place the jackstands under the frame and the jack under the differential. You will need to be able to raise and lower the differential to get the new mount lined up. Replacing the differential mount is very easy.
The subframe mounts are another story. Technically simple but quite aggravating for the reasons that rs899 mentioned. Getting the large bolt started is easier if you have a bottle jack. Place the jack under the bolt to lift it. Turn the bolt while the jack is pressing the bolt upward. The bolt is tapered to help prevent cross-threading.