(no pippas allowed to look) Helpful Links for the project.
New
I think we may still need a proper experienced Doom coder?
I'm far from being called a coder but I'm someone who played and still plays a lot of classical doom mods(WAD's), if you want to do a Doom mod you probably won't need a coder.
I played a bit with classical Doom modding(I'll post some links on the end) and from what I remember most of it is just basic asset replacement, you use scripting/coding only if you want to change the behaviour(fire-rate, damage, AI, ... not the looks) of enemies/weapons and script objects(NPC's and more).
The problem I see with doom modding is that sourceports began to add extensions over it, like how DSDA lets you have bigger maps, more enemies, more advanced scripting and more, ZDOOM has everything from DSDA plus it let's you do even more advanced scripting, use real 3d models and more but this is something I wouldn't care about it for a pippa project, I would just go to the easiest(ZDoom).
Now some links:
The WAD Editor I used was the SLADE3
There's doombuilder too that aparently works better with ZDOOM, DOOMBUILDER
The DSDA-docs for wads are on it's github
ZDoom docs
Doomwiki Forum post that could help: [Vanilla Level Editing] Lesson 1: Preliminary Reconnaissance