Are you expecting some sort of flippent installation tutorial?
No, screw that I'm making this a simple and easy to follow tutorial, god damnit!



to install simply open the folder of the item you wish it to replace. then take the tf folder to 
Steam\SteamApps\<your username>\team fortress 2\

it will ask you to merge, just say yes.



Now Uninstalling is totes easy. You just find these folders:

team fortress 2\tf\materials\models\player\items\scout
team fortress 2\tf\models\player\items\scout

remove these files respectivly 

spiro_pendant.vmt / .vtf
spiro_pendant_normal.vtf


scout_medallion / hwn_scout_misc1




NOTE: if you do manage to have the brass to use this one model to replace both of them,
you can do this by dragging BOTH tf folders from both files into the same

team\SteamApps\<your username>\team fortress 2\
