I don't think I would cut the top out at this point. If you have
time, I would just wait it out for a while and see what develops.
Then if after a while you have healthy, new lower growth and the top
is still dead, you could cut the top out and still have a nice tree.
Another option might be to select a smaller tree. The little ones
(1-2 ft. tall) have a much better survival rate. They grow fast, so
you won't have to wait forever to have a nice tree. Also, in my
experience of transplanting aspen trees from the Rocky Mtns., it
seems that they do better if you can get a small clump of about 3
trees.
BTW - Be sure to get permission before taking trees from private
property or public lands, to avoid hefty fines, jail, other hassles,
etc.
Hope this is helpful.
Gary