(Just noticed the title doesn't make sense supposed to say "A few question on what i should do after my service a today and the dealer" didnt want to make another thread)

I was the one that couldn't get my oil filler cap off so I had my Service A done today and used a $100 coupon on it. Came out to $67. They also replaced my cam sensor solenoids under a recall that I never received a letter or email on.

Anyways, the service advisor told me I needed my control arm bushing replaced. He quoted me $380 and I first thought that was going to be the cost for both sides, I was wrong it was just for the left side. I don't notice any problem steering or going over bumps (which michigan roads have a lot of). Only thing I noticed is that my car kind of vibrates at 70mph+ on the highway. Could this be because of the bushing or could my tires have flat spots or rims be bent (which I inspected and they seem fine)?

Also have a question for anyone else that takes their car to the dealer regularly....Does it seem that they go buy the manual on things or do they actually check what needs to be done..by this I mean, I changed my air filter last summer before I stored my car and I also had my coolant changed. I had a service B done last summer after I did those 2 tasks and they told me that I needed my air filter and my coolant changed.....Today they told me the same thing and I told the guy No. I changed the air filter myself and had my coolant changed by somebody I know. He kind of got quiet and then when I checked my service release paper he had them checked off green. So I'm kind of skeptical whether or not they even check things since I always take my car to them and they think they know everything thats been done to it.

I forgot to add the service advisor also told me that my car battery is bad yet I see know signs of it failing (knock on wood)....What should I look for?