Front Drive Line: Better to Rebuild or Replace

[MyMach5]

My front drive line has about 1/8" of play in the middle joint (the one that allows it to extend with suspension travel...sorry don't know the name of the joint). I'm getting a pretty good vibration in 4x4 and I'm guessing this is the cause. So, I have a couple questions:

1. Is there a significant advantage to replacing the drive line with a new one rather than rebuilding the existing one?

2. I just put a 4" lift on the truck. If I'm going to replace/rebuild the drive line, would it make sense to have it lengthened to match the lift?

Thanks in advance for the help.