I am always getting people trying to rip me off. Luckily, I know my stuff and call them out on it. Ask around people you know to see if they have "honest" repair shops. The place I go for tires and brakes is actually a Sears store. Not always known for honesty, but this paticular one is.
Ask them to show you the problem in the exhaust. The brake prices are way to high. I got new front pads and rotors on my car for less. Rear brake job was even cheaper than the front. If they say you need new rotors, tell them to measure them and show you the book of discard specs. If they are well above discard spec, they can be turned. I doubt you wore out brake pads in 12k miles.
Vibration in the front at highway speeds is related to the new tires. They are not balanced right. Or you could have one of several common problems seen after new tire installation: a bent rim that is showing itself now that there is a new tire not worn to it, an out of round tire, or they need to try to turn the tire on the wheel so the heavy spot of the tire and rim are opposite each other. (I spent 6 years selling brakes, tires, suspension parts.)
Good luck on the second opinions. It may not even hurt to have a third.
