Question about Insurance in California

Hi yall,

I went to the orthodontist recently and was recommended for Jaw surgery because hiding my underbite/crossbite would only be a temporary fix. I also got insight from my friend whose doing his residency rn as a oral and maxillofacial surgeon. I can confirm that I indeed need a LSJ or DSJ once I have my consulting done next week. I had a question about insurance and coverage in California.

I'm currently with United Healthcare Select Plus Gold PPO. I've heard horror stories with getting it approved with United and was wondering if anyone had any issues. I was thinking of buying a separate insurance with Kaiser for the purpose of it. My current underbite/crossbite affects my teeth and my dentist say I will wear it down fast and potentially need replacement teeth in the future. Additionally, I have mild sleep apnea but no studies or history to show medically. I also do have issues where I bite the inside of my red cheek which causes bleeding sometimes.

Any help would be nice.