On my trucks I generally go with Bilstein. On my Taurus and more than likely my G6 when the time comes, I'll go with Monroe. Well made, decently priced and I've had good luck with them in the past on other vehicles. No shock made will last a lifetime, so don't believe the marketing hype you read with lifetime warranty on parts. If it fails, and you take it back in, they'll replace the $40 shock at no charge, and charge you $125 in labour costs....
A PS flush is always a good idea, especially if the fluid is a very dark black. The sediments will settle toward the bottom, in the steering rack and the like. A brake fluid flush might also be worth considering if the the brake fluid is very dark and if it wasn't done during your last brake service as I imagine you do a bit of highway miles.
A good way to test for suspension components too, is to walk around the vehicle and place both hands on a corner. Push down on a corner. If the vehicle rebounds and stops right away the shocks are good. If the vehicle continues to bounce up and down, even very slowly, the shocks are long expired.
