The front axle I bought for my Duramax had 206k on it and the wheel bearings were fine. I wouldn't replace them unless they have some slack in them. Especially with how much of a pain in the ass it is to get that mean ass snap ring off of the stub shaft!
I second Mevotech. I'm using their ball joints, tie rod ends, and drag link ends. I ran Moog to begin with and they shit the bed in about 20k miles.
The only u joints I'll use are Spicer.
As for the ass vibration, I'd check rear driveshaft u joints, carrier bearing if it's a two piece shaft, or even try balancing the tires.
