Can't answer question #1 for you, but as for #2 and #3...
#2 - Might ask around this and a few other G.I.Joe-related boards to see if any convention-goers are interested in it. The tricky part might be arranging a meeting AT the Convention.
#3 - Three random thoughts on this. Find some charitable dealer who's willing to share table space (this could be tricky given the size of the Terror-Drome and for all I know might be against Dealer's Room rules); There have been at some Conventions in the past bulletin boards where you can tack small notices. Again, I don't know if offering something for sale might be a violation of the rules for this; You could walk into the Dealer's Room and say in a loud voice, "YO, GOT A TERROR-DROME FOR SALE OVER HERE!"
EDIT: Just a thought if you can't sell the entire Terror-Drome, you might try to sell it off piece-meal, to people who need parts for repairs. Like -- me...
Best of luck. Enjoy the Convention, whether you manage to sell it or not.