You would have to extract the model files from the gcf. So go into GCFScape, into the tf2 content gcf, and search the model name, with an asterisk at the end, and check wild cards. (eg. the model name is rock004.mdl... you would go in and search rock004* and check the use wild cards). This gets you a bunch of files like a .mdl, a .phys, etc. You need to extract these, to say your desktop or other convenient location.
Next what you do is go back to GCFScape, but this time go into tf2 materials gcf. then do the same wildcard search, and you'll get 2 files, <modelname>.vtf and <modelname>.vmt, extract these to the same place as you did with the model files.
Due to the limitations of a hex editor, which we will use soon, you have to rename the file, with the same amount of characters. so if i was renaming rock004, i might do jrock04, which still has 7 characters.
Now replace the <modelname>.vtf with the edited one (use vtfedit in case you don't know how to make it into an editable file).
Then you need that hex editor to get the model file to know what texture to use. I use
XVI So open the <modelname>.mdl with it. You need to change 2 things. First the top part of it, there should be a path to the file. edit the filename to your changed filename. Next is near the bottom. After "Body", there should be the filename, and then the file path. edit the file name to your changed one.
Now we need to put these models in the correct location for hammer to use. So in the hammer model view you could find out the path for the model. Lets use rock004 again. Rock004 "model files" which is everything but the .vtf and the .vmt, need to go into the tf/models/props_mining folder. The textures need to go into tf/materials/models/prop_mining
Hopefully after all of this it should work! And i really need to write a tutorial i can reference people to rather than try to explain it each time
But those are my issues.
