you're wrong luberone.

The upper A arm ball joints are not replacable because they are part of the A arm.

The lower ball joint that goes into the LCA is replaceable. You have to remove the hub from the car to replace it, but it can be done (I did mine not too long ago).

Now, as for the grease:
If you look at the top of the boot, there's a metal spring keeper that goes around the whole thing. Remove that and you can slide the boot off to put more grease in there.

hih