ok so ive been looking aroumd for so long and i am hoping someone can help me retexture exsiting units mabye just give me a guide i dont want to make a map i just want to retexture people any help is appreciated

(to be clear im not retying to make a map) ok so i already have tried munging my newly retextured units then replaced the rep file in gamedata/data/_lvl_pc/side but then my game crashes after choose my era gamemode and push start. any fixes? also when i was munging it gave me 2 errors im not shure why.