It isn't enough to just know the name of the company that is providing the insurance. Each company offers all sorts of different programs and options at different levels of coverage and cost. However, most policies I have seen do not cover trans stuff such as hormones. A savvy endo can usually find reasons for them to cover things like blood tests.
I would do a little research on the United Healthcare site for the type of insurances they offer and see if they have one that covers transition related costs, see if you can purchase it and how much it costs. Also see what their requirements are, as they are sometimes different than required by WPATH. My wife's insurance company has a plan that will cover GRS, but they require you to extend your RLE, from the standard 1 year to 2. Ok if you have no other way to pay, but not ok if you have the cash to pay now.
If you can't find the info on the website, call them and ask them flat-out what is covered and how much. It might end up being more than you would pay cash to the doctor.