1. hicas light coming on and clunk = not normal, well at least my car does not do that...
im not sure what it would be but best get a good big service done when purchasing a gtr anyways. although if you have bought off an australian owner might be a bit of a different story.
i spend 1900 on new clutch, timing belt etc just after i bought mine, now runs sweet.
As for the group A, maybe check the VIN number on the net and see what you can find out