Keep in mind, this is a junk alternator that was thrown under the bench.
I start by marking the 3 wires that come from the stator (stiff wires with white insulation on them) I use 3 colors of finger nail polish, err I mean paint pens, then I take a photo of which colors went on which posts. Unsolder 3 wires, 4th wire is not required to unsolder as it stays with the back half. The wires will need to be bend in a straight line so that the back half can be slide off the stator/rotor. I always unsolder before removing the regulator so that when i burn my hand and flick hot solder then it doesnt go inside.
Next remove 6 skrews from the regulator, I use a magnetic skrewdriver. Tap the edge of the regulator with a skrewdriver handle to loosen.
Try not to jab a skrewdriver between the 2 unless you must, it is a machined surface that is easy to ding. The regulator has an O-ring on it also.
When you remove the regulator, there will be 3 wires attached, #1, #2, #5. Just slide them off the posts, the outside of the regulator case is marked which wire goes where.
Next remove the 6 small bolts that hold the back half to the stator, be very cautious when removing these bolts as they have lock washers on them. If you drop a lock washer, it goes straight in the rotor/stator. If that happens they you are taking the rotor out to fish out a lock washer.
I use an old 35mm film container with the top and bottom cut off for the next step. Slide a spacer of some kind, preferably non metallic, over the brass bushing on the shaft, one at a time, slide the spring loaded pickups back with a dental tool then slide your spacer down, there are 2 pickups, one on top of the other.
REMEMBER!!!! when the back half is removed if you dont hold on to your piece of plastic the springs will shoot across the shop.
The snap ring below the brass bushings does not have to be removed if you are just replacing the back half.
Next I put the back half in a vise with a thick rag or piece of leather, then tap the shaft with a soft faced mallet. Nothing hard faced or you will damage the brass, as seen in the photo. Sometimes they just come apart on the bench, other times they can be the red headed step child. When it comes loose just slide the back half off slowly, holding your plastic spacer that is holding back the pickups and springs.
Reassembly is done in reverse. Patience is required when resoldering, dont want any overflow to touch another post, I use a piece of hard plastic to segregate the other posts that I am not soldering.