At the beginning stages of bearing wear, the symptoms would be a loud roar when spinning and not necessarily side to side play. You are on the correct track with replacing the outer tub halve seal, I always find the glued seam of it and place at top of washer vs the bottom. There are a few concerns with the spider. One, is it seized tight against the bearings which would require you to beat it out and possibly mushroom the end of axle. You can remove the rotor BOLT (17mm) and push forward on the shaft to see if it is free or not. In my experience, they either slide forward with nearly zero effort or require a BFH(thor) to remove thus ruining the end (I didnt take precaution not to ruin). 2nd concern is the integrity of the spider. I would turn the tub every 30 degrees or so on a full revolution or two and pull up hard from the 6 o clock position to check for cracks. Last concern would be the ability to remove the 6 or so spider to tub bolts without snapping them. If you do snap them you need new bolts and to drill them down far enough to pop the spider off. As a pro, these jobs get quoted a rear outer tub WITH bearings and a new inner tub (Lifetime warranty on part providing POP and finding an ASC) to ensure proper repair without hangup.