Michael,
Yes, I think the rebuild kits are sold only in pairs but they are less than $100 per pair(top and bottom), just check with Buds or the other reliable suppliers. If you need to remove the outer/upper then yes, you will have to have the car realigned. But best to try first to just replace the zerks without even touching the CA (just replace the one in the upper/inner CA and the one on top of the king pin), if I assume correctly that those are the ones not taking grease. If that doesn't fix the problem then you will need to install the rebuild kits.
If the boot you refer to on the lower CA is the little seal that Jim shows on his pic (what a helpful diagram!) then you can probably find a suitable rubber washer or slice of hose if you want to avoid the lower CA rebuild kit. But I think you will have some trouble getting it right, the original seal is a flexible little sucker with an "accordian" action that lets you squeeze it into place and causes it to acheive a good seal once intalled.
That said, this is a very straighforward job, lots of helpful posts to get you through it if you choose to tackle it yourself.
Best,
g
'64 230sl, fully sorted out...ooops, spoke too soon