You don't have to take it completely apart. Once you have the axle out you can get to it, BUT like you said you may want to go further and tear the complete assy apart and inspect it.
I would recommend the knuckle rebuild kits.
http://www.marlincrawler.com/htm/axles.htm
On the studs, I am going to say no, unless you are having a problem with them.
The bushing are most often in good shape. Check for play and scoring.
Remmember if grease is leaking out, water and dirt could be getting in.
BTW
