One of the best ways to disassemble a timber frame is to do it in the reverse order that it was assembled. After you remove all the boards from roof and walls, then remove any purlins and then rafters. After the rafters with proper bracing as mentioned remove the plates (these 36' long beams).

You'll have to make a peg pusher to push the pegs out and release all the joints as you go.

Sometimes long timbers like this require the use of two gin poles at the same time, and lots of hands to help.
You'll have to raise it carefully and evenly and then lower it the same way. Once lowered you can carefully inspect it and determine the amount of damage done.
If these timbers are plates then they can be repaired with scarf joints.
Good luck,
Jim