I need to change of the differential carrier bushings (two rear ones) and I am not exactly sure how to do this.  Do I need to take the rear spring loose as well in order to not have any pressure on them bushings.  Can I do one side and then do the other.  I do not want to take everything loose unless I have to.

Are you talking about the two outer crossmember(batwing) cushions/mounts, or the front diff mount cushions?
The front diff cushions are not that difficult to do, but the diff mount(batwing) on yours might need to be loosened to allow a little room.
The two crossmember/batwing cushions are gonna be really hard to do without dropping the entire diff assy down. I'll say that I have never replaced those in that type of diff with it in the car, so I don't really know how difficult it may be. You will need to take the bolt out of the front diff mount(snubber), and possibly disconnect the driveshaft from the diff to keep from damaging the u-joint. Not sure how far down the diff assy will go before the driveshaft hits on the frame.
 You may be lucky enough to get one side of the "batwing" down far enough without taking anything loose other than the bolt on that side...as I say...I've never tried to do that.
Adams' Apple2011-04-10 08:23:53

Finally got one of the bushing out today and what a pain.  Took the spring loose on both sides and removed the batwing bolts.  Raise one side and lower the other forced the old bushing out.

Now to the next problem.  I can get the front side of the bushing pulled in as the leading edge of the carrier is chamfered and it pulls right in.  The back side is a straight fit and the bushing is too big to start into the hole.  It is about .150 bigger thann the hole and with no leading edge chamfer it will be next to impossible to get it started.  Any ideas how to get this thing in?

Read somewhere on another site that they chamfered the leading edge of the batwing to get the bushings in.  Could I do the same thing with the bushing?  Getting someting into the area while still attached to the car is not going to be easy.  Plus there is a raised lip that would need to be ground off first before you could even get to the hole.