How to re-skin weapons?

[geoface]

So basically I have a shotgun model, and I found a .dff exporter for 3Ds Max, so

I exported it as a .dff and then used dff2wdr so I could use it in gta iv.

But when I went into the game the gun was slightly larger than normal guns, had

parts of the model missing/deformed and wasn't in niko's hands, plus the textures

I had added weren't present on the model.

What am i doing wrong and does anyone have a tutorial as I was just going on

a guess on how to do this and obviously it was wrong.

If you have a tutorial please PM or leave a comment.

P.S

if anyone has a tut on how to make custom animations for when I'm

holding the weapon i.e reloading please also post