How do I graphically change default weapons only, without all the fluff

So, say I'm using the Doom 3 weapons mod for Zdoom- is there any quick way to make these weapons act completely like the original Doom weapons so as to be compatible with levels and such tailored/ balanced for the old weapons, i.e. just make them graphic/sound replacements?

The most intrusive thing this WAD does is replace most of the ammo in the game with its own- compatibility with everything is screwed, especially if it adds alternate weapons. How can I keep this mod from replacing the original ammo? I have a rudimentary knowledge of DECORATE, so any specific instructions would be welcome.

I think i can help you,
to replace the normal doom sprites with the ones from the doom 3 wad
you will need a program like XWE, take the sprites and sounds from the doom 3 wad, find the ones that you want to replace and, replace.