Insurance: What kind of uphill battle do I face in getting approved?

It depends on the plan.....my plan accepted a letter from my pcp detailing the fact I had been seeing him monthly and he supervised my weight loss attempts.  He was very supportive of me and he recommended surgery all along.  Insurance companies have their own rules - you should ask your insurer what they require....some will accept evidence of attendance at WW, pcp supervision, and some do require a nutritionist.  I called my insurer a few times with questions on their requirements.  

Depends on your plan. Some GP's can do it, others require it through the surgeon's office, others will even take sign-off and/or receipts from places like Weigh****chers. Make sure to ask!

Remember that this will NOT get your weight off "ASAP," even if you have surgery right away and are completely compliant. WLS is not magic. Folks generally lose quickly for the first few weeks, but after that it's most often a slow-and-steady pound or two per week. Posters here with about 100 - 150lb to lose seem to make goal in about a year, those with higher BMI will take longer.

First thing to do ASAP is contact your insurance company and get a list of what they require for approval. It varies a LOT, based on what I've seen here; some people need extensive medical records on weight (I needed 5 years' worth), others don't need it at all. Some plans accept different things as comorbidities. You need to find what YOU will require, and make sure to get it in writing.

From what I've read here over the past few years, very few people get denied on their first attempt. It may take a while to complete all of the requirements, usually the pre-op supervised diet in particular, but there's not usually a significant delay.