I think you need to have some Nitrox knowledge, mainly to understand the theory.
I would chat with several instructors and see which one works for you. They should be able to advise you as to the pre-requisites. I did my MOD 1 with Dave Thompson (write up on RBW Here) and can thoroughly recommend him. He's a nice bloke to boot.
you'll need advanced nitrox, however depending on the instructor you may be able to do that at the same time as the mod1.
Also it may be worthwhile doing rescue diver or an equivelent before you go onto a 'breather.