As has been said above, it's the instructor, not the agency, and very short certification classes are not a good idea. You might want to take a quick look at the thread linked to in my signature line for some discussion of what an OW certification class should be.
It's my personal opinion that a class should run over several weeks, so that you space out your practice sessions and give your brain a chance to absorb stuff. That also allows for some extra time in the pool if you end up having issues with anything, like mask skills or buoyancy control.
Also as said above, fill in your profile, and you will almost certainly be able to get some instructor recommendations for your location. ScubaBoard is an amazing resource for that kind of thing!
I think most shops require that you buy your mask, snorkel and fins. Mask you SHOULD buy, because fit is important and individual. My suggestion is to buy the least expensive fins the shop offers, with the knowledge you will replace them with what you actually want once you are certified. Most shops will try to encourage you to buy the most expensive fins in their lineup. I did, and replaced my $180 fins with $75 fins I like better in less than six months.