hi! thanks for all of your nice comments!
answers to your questions:
i use vegas movie studio 8 as my editing software, but i would advise you to use stop motion pro, its built for animation
for mouth replace ments, search replacement mouths on google, and it should show you a poster of all the replacement mouths you can use, and just build them out of clay. then when you have filmed it all, just fit the lips to the words!
hope that helps