Possible, yes.
Doable by you obviously depends on how well you understand both tkinter and wxPython in order to be able rewrite the GUI.

The best way to start would be to equip youself with a standalone Python 2.4, wxPython 2.8.9.1, and the wxPython demos, so you can explore and experiment.

Once you have some feel for how to do a fairly simple dialog in wxPython, you and start to tackle both the conversion from tkinter and the extra wrinkles involved because you're using wxPython with Poser (by the time you get this far, I should have been able to post some helpful stuff).