Hi,
is the disk hot-swap-able (manual of machine should tell)? If yes, you can just draw it out of the box, BUT -> Is there the rootvg or a part of it (lspv)? Is it mirrored (the vgname that's on the damaged harddisk ->
lsvg -l <vgname>
If there are at least twice the amount of PPs to LPs, there will be a mirror there.
If there is a part of the rootvg on it and it's not mirrored, you'll have a problem.
What AIX do you use? How did you notice, that a harddrive is damaged? What does "errpt -a -dH" say? What does lsdev -C <harddiskname> tell you?