We needed to do some little repair on the trailer, so after reading this thread and spending a long time thinking how to do it, we decided a crane was definatly the easiest way.
1. Thats a handy place to have access to
2. Lifted the stern about 2 inches off the trailer and rolled it backwards untill the stern was above the tressles.
3. Make sure the tressles are in the right position and lower it down.
4. Lift the bow and pull the trailer away from under it
5. Lower the bow down onto tressle no. 3
Wasn't as difficult as we thought it would be