what you gotta understand is.. every game most likely has their own storage format
so.. just bacause it has .PAK as the extention doesnt mean it can be opened by any PAK viewer/explorer/extractor
sooo... what you gotta do is figure out how it stores the data, usually done by decoding or understanding the header of the PAK file..
most of the time.. this is where the info you need is stored
usually Byte Offsets, Filesizes, filenames, some other stuff
(and sometimes they are stored at the Tail of the file)
once you know how to read that stuff
you can try to extract the files
from there you need to figure out the image formats
which will likely be some form of DDS compression
modify that image to your likings
then you can try to inject that modified data into the same place you got it from
if all goes well... you'll see what you modified on-screen
unless the data is hashed somehow... then then textures wont load at all
anyways... i dont have spiderman.. otherwise i'd help out...srry