It shouldn't but I haven't tried it myself! I'd keep a back up zip just in case something does get changed you can change it back to how you had it. when i make any sort of modifications to my Feralheart I always ZIP a back up of my current version before installing anything new
This is the solution i found on another thread that somebody said made it work with the same issue as you are having.
Hey Rafe-dreams! You can find a good chunk of the texture files for the characters models in Feralheart>Media>textures>masks! [I also believe that might have been where something is missing]!
When dragging files over i'd def keep my eyes peeled for fmaneLight, fmaneMask, fmaneMask2, fmaneShade. Could be any of those.
If this doesn't help I can download the texture pack you downloaded and take a look at it myself :3
I took a peek at your instagram and my goodness you artwork is amazing! My favorite is the close up of the eyes you posted on the forums here as well <3