Overwriting stock textures

Hey guys, just wondering, how do I overwrite stock game textures? I've altered the texture I want to replace by extracting it with PBO manager (and I've backed up the PBO file), but when I try to replace the PAA file in the PBO with my altered texture, I'm warned that doing so will destroy the file's digital signature (and make the PBO file unusable). Is there a way to replace the PAA file in the PBO without destroying the digital signature, or an alternate method to get the same results?

Thanks :)

I would suggest that you look at using Hidden Selections.

I may be mistaken, but that message pops up when youre trying to replace something in the pbo without it being extracted. Try extracting the pbo to a folder, replace the texture, then repack into a pbo. Should work fine