I can't speak to using WoD in True20 (I haven't tried it yet) but I think I can allay a few of your fears about the damage system.
True20 damage is resolved with a saving throw. This particular save happens to be Toughness, and doesn't automatically scale with level (for PCs). All damage has a static bonus, added to a base difficulty (15) that sets the difficulty of a given toughness save; critical hits add to the damage bonus. Further, the True 20 book includes conversion guidelines between other d20 games and True 20 values (these guidelines aren't great but you do what you can).
So, unless the magic system of MCWoD does something really, really, really bizarre damage-wise, it should work pretty smoothly in True 20.
(Another place you may get a good response to this question is on the
True 20 forums, where most of the posters are friendly, and the chances are high that someone has actually attempted this exact thing.)
Good luck, and I hope that helped some.