The format on most cards (or all the ones I’ve used) can be viewed in windows and deleted in the same way. If you don’t have a way to get the card viewable as a drive on your computer, then I’d consider buying the cheapest memory card available for the camera, and keeping that for your own use rather than using your dads and worrying about whether it’s properly deleted.
With regard to the vein, although it’s not as deep as feared, it might still be a little far for the oil to reach going by what’s been said on this thread. I would look out for what Sparky reports back regarding dmso. I might even temporarily occlude the target area (for a few minutes) to give it first shot at what ever actives were used.