aye, im doing this aswell but im going to use a frige frezzer, and use the top for a veg room and the bottem for my flowering room. At the moment i have striped the fridge down, going to use a 250w light in the flowering room. For ventelation im going to place a vent at the bottem of the fridge door and a rather big computer fan at the back of the frige where the light is to suck air out but also to help suck heat out of the fridge. In your case i'd vent the fan to your outlet of the back of your dryer (if you have one) i plan on doing some tests first to figure out a nice way of mantaining a nice 25degree in there.

i recon it will work well, heres some other help here