Help with Medicare questions.

Open and laparoscopic Roux-en-Y gastric bypass (RYGBP), open and laparoscopic Biliopancreatic Diversion with Duodenal Switch (BPD/DS), and laparoscopic adjustable gastric banding (LAGB) are covered for Medicare beneficiaries who have a body-mass index >35, have at least one co-morbidity related to obesity, and have been previously unsuccessful with medical treatment for obesity. These procedures are only covered when performed at facilities that are: (1) certified by the American College of Surgeons as a Level 1 Bariatric Surgery Center (program standards and requirements in effect on February 15, 2006); or (2) certified by the American Society for Bariatric Surgery as a Bariatric Surgery Center of Excellence (program standards and requirements in effect on February 15, 2006).  And Aetna told me that they follow Medicares guildlines. My problem is NO ONE has been able to tell me what is the process for going about getting this done. My BMI is 48 and I have a few of the co-morbidities. But the "have been previously unsuccessful with medical treatment for obesity." what does that include?  Yes I have tired dieting in the past.  Yes my doctor had me try xenical.  I tried Weigh****chers etc.... As for the medical center part we are fine in Phoenix since we have 3 approved.   Also does the surgery need to be pre-approved? Thanks....