My factory Service Manual says this job cannot be done without taking the unit out of the car and dismantling it, because of the need to replace the collapsible spacer every time, and to ensure proper backlash and tooth meshing; that’s the factory approved methodical approach.
The Haynes manual says otherwise, their method being to not replace the spacer (aka crush sleeve). Haynes describes duplicating the original torque and position of the nut.
Either way, the goal is to get the backlash in the gears down to a very small amount, but not zero.
Since you are starting with a situation where the work performed by the outsider is unknown, you should probably assume that the crush sleeve is questionable.
A crush sleeve acts like a spring of very short travel, like only a few thousandths of an inch, pushing the inner roller bearing away from the outer race.
When you get the flange and seal off, you may find the tapered roller bearing is too tight on the shaft and won’t just come out like a front wheel bearing.
But if you can get it out, you may want to try to remove the crush sleeve if you can get some kind of hook tool behind it.
The torque on the nut is 120 to 140 foot pounds while rotating the flange to ensure correct seating of the bearings, but that’s with a new crush sleeve.
With an old sleeve, you will be limited to feeling the backlash and stopping before you think you will go too far.
BTW earlier models have an axle with a solid spacer tube and shims rather than the crush sleeve.