Need Advice

I'm in my late twenties and I believe I have a class III underbite,
(whatever this means.) Initially, I went to see someone (under my PPO
plan) for Invisalign consultation for misaligned teeth. After taking
my x-rays, the DDS told me I do not qualify for Invisalign and that I
would need traditional braces, accompanied by surgery to fix my
underbite. He seemed very professional and I would actually consider
getting work done from him. But I need a second opinion. And before I
setup my appointment elsewhere for a second opinion, I need to arm
myself with some knowledge.

He wants to charge me negotiated to ($75 bucks) for impressions/molds
and states that it is "separate" from my insurance and insurance will
not cover that. Is this customary/common, and can I expect the same
out of pocket cost elsewhere?
How long do you think my case will last and cost for me?
Thanks a lot