Hacking How do game mods work?

[SK91]

My PSVita is on 3.68 with h-encore. I'm trying to mod a European NoNpDRM version of Persona 4 Golden (The mods in question give me a free camera, and the other mod turns Yosuke into a hardcore weed addict)
for Persona games specifically there's a tool made by TGEnigma and Shrinefox called the mod compendium, in the case of Persona 4 Golden you use a VPK from the game and patch it with the mods, it makes a new VPK and you can use it in the patch/rePatch folder (not clear on the patch and rePatch stuff)

I think the problem lies within decrypting the game. I can't seem to find a good way to do that. CriPakGUI does nothing with the data.vpk file I took directly with the game. Psvpfsparser doesn't even start up correctly without giving me an error and closing. And from what I can tell the vitashell decrypt doesn't look any different (yes, I checked the hex of eboot.bin)

I believe the mod compendium uses a specific vpk file from the data.vpk (don't quote me on that it sounds weird)
but yeah. If anyone wants to try figure it out you can find all you need at shrinefox.com