You have to be a contortionist of the world class, to be able to get to ISS splines in any "I can work on it" position. I tried. A;lso, ISS splines are sealed from the top with a rubber seal and entire clearance to place anything inside is MINUSCULE, so you need a syringe with thin needle and it has to be bent to poke through the seal squirt some lubricant in.
What dealer does, they "milk" the shaft. It has plenty of grease as is, it simply is not distributed across the splines on its own. So they disconnect upper shaft U-joint, and collapse ISS onto itself. They do this manually few times, up and down, so splines are re greased. Motion is similar to milking a cow, hence the term.
Good luck with that. Like I said, the only way you can get to it is to move seat all the way back, lay on your back, get plenty of light and maybe then, you can get to the U-joint bolt. It's not really that much of a job, it's getting to the job site that is tough.
Folks come up with all kinds of ideas how to secure steering wheel during this, as you do not want it to spin. Most tie seat belt super tight around SW, securing it in place. If you have SW secured and not moved a bit, and you remove ISS, nothing is changed in steering configuration and alignment is not needed. If SW moved and you ended with crooked wheel, alignment is not going to fix it anyway, as you simply have properly positioned steering rack but SW is crooked on it. So it needs to be undone and rotated to proper position. As I said - good luck. Doable, but RPITA. Simply because of very uncomfortable job site.