You'd be better off to wait until spring, or at least until the leaves fall & the tree is resting. You didn't mention how large the tree is, but you should be able to lift & bare-root, then plant in the gritty mix - soon, as long as you can protect the roots from freezing - spring, if you can't. I'm not concerned about frozen soil killing the tree, but roots of different age class are not equally hardy. If you transplant into a pot in fall, you should be sure to protect the fine roots that will form after the transplant - or wait.

Al