1) There's alot of info
2) I'm confused
As this is my first post, I feel compelled to start with a short introduction:
I'm a programmer at a webhosting company. I have a degree in Graphics Design, which basically boils down to: I have 10 hours training in 3D Studio Max and $30K debt (which means I can't afford 3D Studio Max). The very first ever FPS style game I've EVER played on a PC is Portal. I, too, was entranced by the Companion Cube, and felt the game was too short.
However, I seem to have a personal storyline for the game that is much darker and sinister than I've seen elsewhere. Maybe we can talk about that elsewhere.
Now, with that out of the way...
I (like many other people) have an idea for a Portal mod. I've read the Portal docs on the Valve community site (as many as I can find), and read just about everything I can on this site's wiki, and a few other sites. I have installed the new SDK into my Steam, and given all the programs a once over.
I'm COMPLETELY NEW to the whole level building/modding idea. I feel like I have steps 5-50 in my head... I just lack steps 1-4.
So, my opening shot at the community is this:
1) Are there some really simple tutorials on getting a level togeather for Portal (I thought I found some two weeks ago(?) but naturally forgot to bookmark them). I'm talking "See spot run" here. I can model some 3D pretty decently, but I'm a bit rusty. (3d Environments, not so much 3D people...)
2) I tried using the Source SDK to "Create A Mod", only to get an error (to the general gist that I can make Engine 1 mods with this SDK, but not Orange Box Engine mods... and as Portal is the only game I have installed this don't work). Then again, maybe I'm getting ahead of myself?
3) The eventual goal is to end up with a story based Mod, based on Portal*. I plan to build some environments for it, while getting some rooms as donations. 'Course, I want to make a playable demo first, hence 1 and 2 above.
- The story follows a test subject in the "Aperture Science Enrichment Center -- Tokyo Annex", with a completely different testing computer (I'm thinking GLaIX, a play on the type of UNIX kits made in the DOS days), and a completely different set of puzzles, but with more delving into the backstory of Aperture Science. Right now it's in the "Me and my friends think this would be cool" stage, and I plan on working the details out whilst taking care of 1 and 2 above.
To make a long post long, I'm completely new to this, and most of the stuff I've found so far assumes at least a basic level of modding knowledge, which I completely and utterly lack. All I've got is a good idea (IMHO), some fire to do it, and a willingness to learn HOW to do it. My mod idea is less "hey, this type of room would be cool" or "hey, I want to build a puzzle where you have to do a, b, and c", and more, "hey, you know what would be really cool? If the story was more like this, and you get the hints in between rooms." So, I'm not quite sure what the rooms will contain, whereas I have more ideas about what you can do outside the rooms. If that makes sense.
Anyway, can't wait to get a bit more involved around here and start making things.

I advise you to start here: