AP racing front disk replacement

[MisterCorn]

I am changing the pads on the front of my car, it is fitted with a 6 piston AP racing setup which so far as I can tell the disks were originally 32mm thickness. They are now measuring at just over 30mm. I can't find a spec for the disks which is the first issue.

Assuming that they are ready for changing, I think the part numbers are

CP7177-110G8
CP7177-111G8

But I am also seeing references to part numbers

CP3581-536G8
CP3581-537G8

As I haven't changed these before I have a couple of questions...

Does anybody know the wear limit on these?
How do I tell which disk is the correct one?
Where is a good place to buy them?
Is the disk mounting hardware routinely changed with the disks?

Thanks for any pointers.
MC