Looking for Tutorial on how to Replace Weapon models with my own.

[Dark Session]

Long story short, i love 3D Modeling and got some things working. But im looking for a guide on how to get the Models into the game. For example i want to replace the Fireaxe in L4D2 with my own model. I watched some videos on youtube but they are either not voiced or horrible complicated and outdated. I even just want to get the model into the game, first without textures to see how it looks like ingame.

I use 3DSMax 2019 and those SMD Exporter/Importer plugins seem not to work anymore. Heres my model :

[url=http://abload.de/image.php?img=3dsmax40p05.png][img]https://abload.de/thumb/3dsmax40p05.png[/img][/url]

Help is appreciated!