So maybe you've been reading my site and your thinking that you would like to mod Doom. Well first you need Doom II, once you have that you could use a number of utilities to mod doom. This page is a link library to.
Doom builder is the absolute best doom map builder in my opinion. Not only is it easy to use, but you can download a manual that tells you how to build everything. Also doombuilder is compatible with almost all of the popular source ports.
Get it at www.doombuilder.com
Doom builder 2 is the best of the doombuilders, but has higher system requirments so if your still using windows 95 you might want to stick with doombuilder 1. Although I doubt that will work either.
Get it at www.doombuilder.com
Ok so you've got your maps but how about changeing the way things look. With a little practice you can use Wintex to do this.
Get all of the wintex programs here