Tozan
Overlander
I would replace it. All of these spacer lifts ruin the ball joint angles and they don't drive very well and wear the joints out faster. The control arms made for the lift should fix both of those things.
This really depends on the kit.. "All" is certainly not true. I am running a Rancho 4 inch spacer lift and it comes with new spindles that take care of the ball joint angles. Mine drives great even up to 80 mph across desert roads and behaves great on highways up to 115 mph.
I also have over 10 inches of wheel travel in the front.