Is this something I need to replace immediately?

 

It really seams to drive fine, it was shaking on ooccasion, not consistently though, I'm thinking that was the CV axle that was failing, which is now replaced. Going to test it though.

Anything special the boot is supposed to contain/protect?

jack up the car so the tires are off the ground.  grab the front and back of the tire and check to see if it makes noise and/or has slop when you twist the tire.  if so then it needs to be replaced.  can be serious so don't let it get too bad.  if they fail and actually break then your wheels will turn independently and might yank you into the ditch or into the other lane.  generally has to get really bad for that to happen, but you never know.  

 

if theres no play or noise and its got tight steering, then clean it up, add some grease, and fix the boot.

Thanks, will do.