Replacing the solenoid requires removing the carrier.
- You MUST keep the bearing caps on the same sides, and oriented the same.
- You will probably need an axle spreader to get the carrier out.
- You must keep track of the carrier shims AND the carrier bearing cups. I'd try to keep them in the exact same order/position. Order isn't as important as side-to-side position - this determines your ring gear backlash and your contact pattern.
- You will need to press one of the bearings off the carrier to get to the solenoid. Once you swap it (and swap your spacer over) you'll need to press the same bearing back on. A shop might charge you $10-20 for this if you bring it to them.
- You'll probably need that axle spreader (again) to get the carrier back in, with the bearing cups and shims in their correct spot.
- Then, properly re-torque the bearing caps to 80 ft-lb. (again, in the same positions they were removed from, in the same orientation.)
If I were you, I would consider measuring ring gear backlash before disassembling, at a minimum, to make sure it's the same when you re-assemble. If it's not the same, you know you have a problem before you go to run the axle and grenade it.
If you've been thinking about freshening up the axle with new bearings and/or re-gearing, this would be a great time. You're already going to be in there. But, it is more complicated since you'll need to set preload/backlash, and get the pattern right.