Hi BIG.
I have no personal experience of this but it is very commonly done here in France - last autumn my neighbour took a twig (scion is the correct term :mrgreen: ) off a knackered old cherry tree of ours and grafted it onto a new rootstock.
With apples, I do know that one of the purposes of grafting is to dwarf the tree so that the fruit is more accessible and it fruits earlier in it's life, so you would need to bear this in mind when chosing what rootstock to use. In England, they are graded by the letter M and a number, don't know if it's the same in the US.
It sounds like this tree is worth regenerating so I'd give it a try if I were you; here's a link with the how tos -
http://www.ehow.com/how_2042618_graft-fruit-trees.html
Hope it helps. :D