I agree with Hobbit, the only way to do it is to remove the swivel and hub as a whole, a little heavy but the best way to do the job.
As for the Bluing, don't worry! Is it even all around? is it a nice elliptical pattern radiating from the centre of the land? It's probably been there since manufacture because the races are ground, they may also be induction hardened. Both of which make the pretty blue and purple patterns. If it's brownish right next to the running surface then it's hardening. If you can't feel any clicking or roughness in the CV then it's fine.
The LR workshop manual does descrive the procedure to strip and check the insides of a joint but given the possibilities for all the bits to go everywhere and come back covered in doghair I wouldn't bother. If it's Knack'ed get a good S.H one or stump up the price of a new one from Paddocks.