my buddy is a reputable one and he's from Greenville, MS. Go figure. He's taken down one of the Bush daughters, Bill O'Reilly and his buds (while Bill was the only one to ride down on a horse), and many many more.
He has everything you need. You set it up with him or someone else he recommends if he's not available. You buy your stuff there (Flagstaff for us). We were in the canyon for 3 days, so we had to buy dehydrated foods, powder gatorade, some fantastic trail mix he mixed up, and 4 beers a piece. 2 For the first night kept cold by frozen foods we took and 2 for the next night we chilled in the river. After hiking all day, you only need 2 beers to pass out. The nights are awesome. You can't have a fire but you don't really need it if the moon is out. I know it's already passed, but May is probably the best. October maybe?
If you are there for multiple days and must get dehydrated foods, get some flavor cubes; chicken or beef bouillon. Your guide should have everything as far as first aid and water filter or iodine pills.
I imagine if you have your own equipment, you can run it by the guide to see if it will do. Sleeping bags, air pad, comfy hip resting back pack, and most important - shoes. Your shoes and trek poles are your best friend. I bought a new pair of Vasque's for this trip. Do a lot of squats and walks or any kind of aerobics before you go.
I know I've rambled a lot but I can PM you more info if you want and get my friends number for you. Best of all, he's an MSU grad.
He took us down GrandView, to Tonto, and New Hance Trail (if I remember the names correctly). They call the New Hance the death march. It's rough.
PS - he makes killer omlets the first morning.