How to recompile a VERY OLD L4D Model to Gmod?

I do apologise in advance for this extremely stupid request, but I have searched online all day and I can’t find a single guide that can make this work

I have the original VPK with the materials and models files.

I added it to Gmod and some textures are missing textures and I can see through the model in some … uhm… places.

I can share the files with anyone if they want to take a shot at it.

http://facepunch.com/forumdisplay.php?f=40 Modelling forum is there.

Thanks Robotboy655. I didnt know that forum exists.