yes, pull the seal housing and replace the o-ring behind the cover, and this will make seal replacement easier, and you can see it better. the pic of the spur shaft cover may be caused by the heavy rust. being from Maine I am familiar with the effects of road salt in the winter. plus, I'm sure that truck hauled salt a few times, check that cover for holes. The rubber thing I mentioned is the ring you see on the yoke.. I was taught to throw that away. I was hoping for other opinions on that one. The main bolt is supposed to be replaced. Mack # 3AX 1803... make sure it has a good dose of lock tite on it. it torques to 500 lbft.. And replace the u-joint straps as well. This is not a technical job, just may have a bit of labor, to get the yoke off. You got this, Jojo