2002 Chevy Astro Idler and Pitman arms replacement

I have a 2002 Chevy Astro with 46800 miles on it. I am a US Serviceman who has been reassigned from the West Coast to Washington DC on the East Coast, so I will have to drive my family clear across the US in my Astro. In preparation, I stopped at Aaron's Automotive in Vacaville CA for a full inspection to get the car ready. One of the items noted in the inspection is that the front idler and pitman arms are bad and need replaced at a cost of over $800. I asked how the mechanic came to that determination and he showed me that when he moved the front tire back and forth with his hands (while it was on the lift) the steering will did not move at exactly the same time, indicating that there is some play before the steering wheel will turn. He also showed me underneath the vehicle that the arms should move up and down, not side to side (I may have that backwards) which could be why my tires are worn unevenly. Before I dump a wad of cash into this problem, is it really a problem, or is a little play/delay between tire movement and steering wheel response normal?
Additionally, when I apply my brakes, the front brakes squeal (uneven sound) when I apply them. The same mechanic said my front discs/rotors are slightly grooved and that the brake shoes are nice and thick but appear old, which he says could be causing the grooving. He said the front discs were dry, so he lubricated them to make the squeal go away. It lasted about a mile before the squeal came back.
For the rear brakes, he said they were fine, but needed some adjustment (Aaron's installed the rear brakes back in August 2008), which he did. When I drove away, I heard a low rumble coming from the rear of the vehicle which I never heard before, so I took it back. He said he might have over adjusted them, so he readjusted. On my way home, I heard the low rumble from the rear again when I applied the brakes. I asked him how to determine the appropriate adjustment. He said that when he spins the wheel with his hand, the wheel should spin freely 1.5 revolutions, but that it is hard to tell with AWD vehicles due to them being linked to the front wheels. Is this true or is there some more accurate method?
I just want to know what, exactly, I really need to do to prepare my vehicle for such a long journey over mountains, through the plains, in hot summer weather to get us safely to our destination.
Lastly, I'm due for a lube and oil change, fluids top-off, new tires (I assume alignment and camber adjustment will be needed for that), which I plan to do tomorrow, but what about changing out belts, plugs, and wires? The car only has 46800 miles on it with, so far, mainly city driving, but many of these components have probably been on the car since I bought it new in 2002.
Would I be better off going to the more expensive Chevy Dealership's automotive center? Would they know more and do it better? I would appreciate any guidance you may be able to provide. The only warranty I have left is the 10 year 10,000 mile power train warranty.