Fallout 1 mod FO 1 and 2 item modding Guide?

Hey I was wondering if it were possible to edit just the items in the world and shops of FO 1 and 2. I saw the big post by Femic which looks like it's more advanced than what I'm actually trying to do. I just wanted to do something like replace a stimpak you'd find in junktown with a gun or something.

I feel like a long time ago I knew how to do something like this and it was basically just editing something like a text file, but I poked around for a while and didn't find anything so I must have been imagining it.

If there are more modding guides for total beginners, I'd appreciate any advice finding the right stuff to learn. I'll dig more into Femic's guide later when I'm not so tired since I just gave it a quick skim and didn't see anything I thought was immediately relevant to my basic needs.

Edit: Poked some more and realized the bis mapper can edit items and stuff. Is this the only method or is there a way to see something like: (pseudo)
"ARROYO\POT_1.dat" with a list of items contained in pot 1 of arroyo.
Bismapper alone works for what I'm trying to do, which is attempt making a randomizer, but it would be way less efficient lol.