How to Insert New Enemy Sprites and Sounds?

So, I'm trying to make a total conversion mod for the original DOOM,and the default enemy sprites and sounds wouldn't be right for the mod. How do I change the sounds and sprites without changing the enemy behaviors? P.S. Using Doom Editor 2 to make mod.

Slade + DeHackEd maybe.

Depends on what you really want to see in your mod.

You need a wad content editor - best is SLADE3. Adding sounds is straightforward, import them as lumps anywhere into the wad outside of any special markers, and preferably convert them to Doom sound format. Instructions for adding custom sprites depend on the intended compatibility of your wad (vanilla / PrBoom-plus / ZDoom), but the general thing to remember is that you need to put them between sprite markers, S_START and S_END (if you wanted vanilla compatibility, it would be more complicated).

To add sounds, simply drag and drop .WAV or .OGG sounds into the WAD file anywhere (excluding sprite/patch/flat lumps). If you wanna add patch/flats/sprites, then do this for the following:

Sprites: S_START, S_END
Patches (wall textures): P_START, P_END
Flats (floor/ceiling textures): F_START, F_END

Put sprites/flats/patches between these certain lumps and for flats and patches, highlight them and right click, mouse over graphics and click "add to TEXTURE1".