Make sure you go to a Can shop.

Whilst that bolt has a 5mm allen key fitment, the thread diameter is actaully 10mm (I think). DO NOT LET ANYONE TRY TO DRILL IT OUT.

Use a 2 pin crank bolt dust cover tool to get the duct cover off the hub first - that way you can see a bit better what you are up against.

Is it a jake? or a DLR? They have AL axles, and have been prone to stripping. They can be fixed quite well with a helicoil. Search the forum.