What a wonderful coincidence that on the day I register here I find this thread.
Wondering why? Well, it's because I have FIRST HAND experience concerning United Health Care and gastric bypass surgery. I am actually 6 months out of surgery myself and have lost ~133 lbs.
Here are UHC's basic requirements to cover GB surgery:
1. DETAILED letter from both GP and bariatric surgeon explaining why the surgery is medically necessary.
2. At least a 5-year documented (like from your chart when they weigh you every time you go to the doctor) history of obesity.
3. There *may* have been a BMI requirement, but based on what you said in your post, your BMI of ~64 would meet it easily.
4. I am pretty sure that is all, but I may have left something out, lol.
It really is not all that difficult of a process to complete, so I will line out the basic steps for you. Your bariatric surgeon (PLEASE do research before choosing one!) will know the nitty-gritty ins and outs better, but this is basically how it worked, at least in my case:
1. My GP told me that I appeared to be a perfect candidate for the surgery. I was 23 at the time with a heigth of 5'8.5" and I topped out at 318 lbs. He referred me to Dr. Robert Davis here in Houston. One of the best bariatric surgeons around. You might have seen his show Big Medicine on TLC.

2. Because UHC requires that letter I mentioned above, your GP should have you undergo a battery of tests to determine if any comorbid conditions exist. For example, I was required to do a nuclear stress test, a sleep study, various ultrasounds of my neck veins/arteries and heart, and, most unpleasently, get an endoscopy/colonoscopy. The reason behind this is the more problems you have, the easier it is to convince the insurance company. You should also meet with a psychologist and a nutrionist who will add their own notes/observations to the packet. I suffered from several comorbid conditions - mainly high blood pressure (was on medication every day), sleep apnea, and severe insomnia. I also had some records of previous failed weight loss attempts.
3. Once all the results are compiled, your GP should forward them along with his letter to your BS, who will then add his own letter and send the whole thing off to UHC.
4. Then the waiting game starts. Luckily everything for mine came back approved within about 2 weeks.
5. After the approval comes in, all that is really left is to get put on your surgeon's schedule.
My surgeon required a liquid diet for the 14 days prior to my surgery. This is to shrink the liver and allow for him to work much easier inside my body. Many surgeons have different ideas/plans for the pre-surgery diet, but most only differ in length - usually anywhere from 3 days to 2 weeks.
So, it may take a little time to get everything together, but after that you shouldn't have any problems.
Also, IIRC, UHC will only pay for 80% of the surgery, so you will have to come out of pocket a few thousand more than likely. Don't let that deter you, what you want to do is a great goal to strive for!
Please let me know if you have any questions and I will do my best to answer them.