If you know a heavy eqpt mechanic w/ a hydraulic crane on his truck it will be very easy. If not, try the following procedure with great care.
OK, first remove the slide, run additional bracing from the bottom of the legs nearest the trees to about the middle of the skids. add more X bracing between those two legs. Drill holes thru the skids on the end nearest the trees large enough to run 3/4" or 1" pipe thru from one skid to the other. Rig a chain around each end of the pipe on the outside of the skids so that it has at least a 45* angle when the later mentioned winch hook is attached to it. Next run a chain or very strong rope between the two trees near the structure several feet above the roof. Now come up with a pickup with a winch. Run the winch cable thru a snatch block centered on the structure on the chain/rope between the two trees and attach the winch hook to the aforementioned chain on the skids. Take a strain on the winch cable enough to lift the weight off the two legs furthest from the trees and cut them off top and bottom. Back the tlr up so the structure will lean over to land on it. Start lowering it just enough so the two remaining legs are starting to bend, then cut them off at a 45* angle next to the ground so that as you lower it onto the tlr the two 4x4's remaining in the ground act as chocks for the two legs you cut off so they can't slide back. You'll have to keep moving the tlr ahead while lowering it to keep the two legs and long braces from touching the tlr until the other end contacts the tlr deck When the two remaining legs touch the back of the tlr, add braces vertical from the tlr deck to the skids close to the two legs. Cut the two legs off next to the skids and remove the long braces. Back the tlr up 'til it touches a tree. With the winch lift the structure enough to remove the two remaining braces and lower it to the tlr. Make sure the rope or chain between the two trees is strong enough to take the strain 'cause it will be greatest just before the structure contacts the trailer. Without a forklift or complete dismantlement this is the only way I see to do it. Just take your time and think ahead at all times!! Just be sure everyone is clear while lowering it to the tlr in case Murphy wants to take over the operation. Hopefully someone else will have a better idea. Sounds awfully redneck but with proper planning and execution I think it will work however the hyd truck crane would be safest.
Mike