cobra/aetna ppo

I am thinking about changing my job and have been looking into COBRA to continue insurance. I have Aetna PPO.  I am almost a month into my surpervised weight loss. My question is has anyone had a problem with getting approval or being approved for surgeryt and then ins not wanting to pay and having a headache to go through. And does it make that big of a difference to do the 6 mo plan apposed to the 3 month? I would like to do the 3 month because it would be sooner and less time on cobra  although I may end up keeping it for the max. amount of time.  Is the documentation more astringent with a 3 month?(I mean things like diet journal or exercise journal etc) I want to know anything and everything you could tell me with your experience with Aetna. I really would like to take this job but  DO NOT want to harm my chances of getting the surgery. By the way, I have already called Aetna and HR and both have told me that the same benefits transfer and that things should be fine...But you know how that can go.Shoulda, woulda, coulda. KIM