I have gone through the Creation Kit site and have a basic-very-basic-don't-actually-know-what-the-heck-I-was-reading-kind of grasp on it so now I'd like to start. Can anyone point me in the direction of a tutorial or something that can help me learn to mod pre-existing houses? I would like to test out some ideas for a starter player house but I would like to make it so it won't break my game or computer and be able to upload it to Steam..I would be super grateful for some help!

The http://tesalliance.org/forums/index.php?/topic/4655-introduction-creation-kit-basics/ sounds like just what you need. Step by step instructions, with a teacher, to creating your first house mod.
Come join the fun.

Thanks! I'm actually super excited to be able to mod. I tried with Morrowind and Oblivion but I'm not very good with technical language. But what you gave me is perfect! :]

If you go to the CK forum, there's a thread with a bunch of video tutorials. I'd strongly recommend not only watching, but following, the official tutorial -- it'll help you figure out a lot of the hotkeys. Then the BIS tutorials are pretty good re-iterations of the same material, and for advanced quest-related stuff, Doughamil's videos are awesome. There's a learning curve though, so take it easy and don't get frustrated.