I just did this on my 2006 500 4x4 (April 7, 2011). I had to jack it way up, first to remove tension from the springs on the shocks so I could get the top bolt out, then even farther so I could swing the shocks to the outer position.
At first I thought I would have to take the bottom end of each shock loose, but I jacked it way up the air and then used a 2x4 about 4' long to pry the tops of the shocks past the tight spot. Then I lowered the jack until the bolt hole was aligned, slipped the bolts in, tightened the nuts, and was done.
I did one side at a time.
I used a big bottle jack under the hitch receiver, and for insurance I had a pair of jack stands under the machine to catch it if the jack failed. There are logical locations for the jack stands if you look at the rear end, about 6" or so to the left and right of the hitch receiver.
The nuts were on the bolts very tightly. Took some real oomph to get them loose. Actually I tapped on a ratchet handle with a hammer to get them loose.