Hi, thanks for the interest, no UCS sets where harmed in the making of the AT-AT as all parts where from Bricklink. Strangley enough i was talking to the Lego Design team the other day but alas an At-AT of this size would be around $2000, they did say that it is more detailed and a little larger than the miniland At-AT's!
As for the framing that was the easy part, if you look back in this thread you will see pictures of the frame.