I've been able to hear a wheel-bearing whine from the rear-right wheel for a while. I went to nip it up a little, but it had already been done up so tight that the split-pin didn't actually sit in any of the recess in the castle nut - so, I bought a pair of rear wheel-bearing kits today.
However, on disassembling the whole lot, I discovered that my rear discs are f**ked:

That's on the inner side of the right disc - as you can see, there is just one narrow band or shinyness.
Also, the pads aren't exactly in great shape - very uneven wear, and I only changed these a few thousand miles ago.

Now, does this mean that I need new rear calipers, or is will cleaning them up sort this out? The rear discs are still nice and thick, so can I keep these without replacing with new items?
If I do need new calipers: Do I have the pre-88 or post-88 items? (My car is E-reg 1988!) Looks to me like they have the external handbrake mechanism... does this mean that if I buy mk3 calipers, I'll need new cables too?

I don't want to stick the new bearings into a pair of discs which are f**ked, so a quick response would be greatly appreciated!
Cheers,
Calum.