I just bought a bit of LFS credit and have turned on the hires skin option. For people who I've already seen online and already have their lo-res skin, do I have to delete my lores downloaded skins, or will LFS redownload the hires versions and overwrite them?

I think the hi-res skins go into a folder called 'skins_y' instead of 'skins_x', so I think you don't need to delete them nor will LFS overwrite them

Quote from Xpowaspa :

I think the hi-res skins go into a folder called 'skins_y' instead of 'skins_x', so I think you don't need to delete them nor will LFS overwrite them

True