hi doc,
A fridge is sort of the prototypical self-contained grow container... I've seen pics of them with veggin gclones in the freezer part and flowerin gin the top!
Using the existing cooling system is kind of meh though... you are MUCH better off to bore a big assed vent hole in the backs of both sections so that not only do you keep the temps down, you also get air exchange, which is ABSOLUTELY necessary. And flouros give off very little heat, so that's a bonus.
I want pics if you do it!!!