I commend you for posting this and wanting to do something about it. My dad was a bit of a hoarder, and I had a friend who was and never let me in her place in the many years I knew her. Wish I could come and help you out. I like sorting out a mess - it's like doing a jigsaw puzzle or Tetris. Spondiferous' method is similar to mine, and lots of good advice here I think. You can do it.

My method is 3 areas - for stuff to keep, stuff to trash and not sure. This quickly sorts everything, and you take out the trash. Feels good. Then you can gradually work through the not sure pile and your thoughts and feelings about those items. If you put the good containers on one side of you and the random cardboard boxes on the other side, you have somewhere to put the good stuff and the trash right away. You have room to work. I'm just itching to get in there. I'm not a neat freak - my place is a little cluttered with whatever we are using regularly, but it is well organized and I can always find what I need. I like to keep a clean workspace in the kitchen all the time, but my husband is a bit clueless about that. He also has craploads of electronics, but I helped him organize them into labelled boxes a while back. At least you have room to work rather than stuff piled to the ceiling that could fall and kill you, like my sister had, so you can get started. And you have motivation. Good for you!