This might be a little late but I bought my CTS-V this way and got three dealers fighting for my business. The owner of the dealership used his personal GM credit card money and applied it towards my vehicle in the end.
http://www.gmbuypower.com, click on the Hummer logo and follow the steps. Find the vehicle you are looking for and start emailing the dealerships with what you want and what you will pay. I would email 5-10 dealers and wait for responses. I narrowed my search to three dealers, picked up the phone and let them fight over me. Remember dealers get credit from GM when they sell a vehicle, the more vehicles they sell the better allotments they get (Limited editions, etc). Its not always about making money on every transaction. Towbin Hummer Las Vegas sells 50+ hummers a month and they have alot of desirable hummers.
I can't tell the discounts on the Hummer but I did look at an Escalade. They were offering GMS pricing - $2500.00 dealer rebate. The dealer also had $500 in holdback money which they can give up if they have to. I would imagine the Hummer is setup the same way. They also were offering 2.9% APR.
I was also told the GMS pricing most likely would be extended, this promotion has killed future month sales, they might be up 40% in June, but how many future months did they steal. Either way the next two days puts the burden on the dealer to sell as many vehicles as they can, we are diffentely in a Buyers market.
Regarding shipping you will have to make the decision to have it shipped covered vs. uncovered (add 850.00 if you want it covered). Uncovered will cost around $1300.00, your lucky that you live in Florida, alot of transport companies have scheduled routes. It will take a 2-3 weeks to get your vehicle.
Hope this helps.