You don't need a laser level. 4' level would work just fine.
Personally, I wouldn't put the posts in concrete for a deck footing. I'd cast a retainer into the footing, then set the post later. IME, the new ACQ stuff kinda sucks compared to CCA. I've got insect damage in months-old ACQ lumber. Fawking carpenter bees weren't phased by it one bit. I'd want to be able to replace boards later without having to unearth an entire footing in order to do it.
Edit: I might as well mention this while I'm at it. MAKE SURE YOU UNDERSTAND HOW TO WORK WITH ACQ LUMBER BEFORE STARTING WORK. ACQ has a very high copper content, and can't be used in contact with any aluminum products. All of your fasteners have to be certified ACQ compliant. That typically means they are coated steel or hot-dipped galvanized fasteners. Be sure to check all of your flashing, hangers, bolts, and fasteners to be sure they are approved for use with ACQ lumber.
As for the post base, go look at the Simpson strong-tie stuff at Home Cheapo. An AB or PB post base is kinda what you're looking for. They've got a bunch of different varieties, so have a look around and find something that works.
Once the footing is cured, you just stand the post up, put a couple of braces on it, and walk it around until it's level and located where you want it. Tape measure and a level is all you need. Make sure you attach the post to the post base according to the post base manufacturer's recommendations. You should be more concerned with uplift from high winds than from bearing the weight of the structure.
As for the footing itself.... how steep is this hill? So long as it's "kinda" level.... 30* or less, it shouldn't be a big deal. Dig the hole plenty deep (2+ feet so there's less chance it walks away with the slope), and check your local codes to see what the minimum bearing area is.... then go bigger than that. Can't really go wrong.
Hell, I've got a small stoop off the back of the house that rests on 4"x8x16 solid precast concrete blocks. It's level there, and those blocks are all that code required for the load I was carrying.
