Go to a frame shop. Have it taken down into 4 pieces of not more than 36" long and a few inches wide. Roll up the contents in a tube. Buy new glass at home. Have a frame shop reassemble it.
Or pack it in a mirror box from a moving supply company, which are double-walled cardboard, protect with bubble wrap and send via Fedex
It is is truly invaluable buy it a seat like a cello.