I think that's a lovely idea; you've already been such a big help to others on the board (myself included; I'm going to start painting Gideon today), it would be wonderful to have your knowledge collected somewhere.
I use Blogger myself; it's an easy enough tool, and since I also have Gmail it was a piece of cake to set up. As far as the actual tutorials, the more pictures the better! That's good advice for any blog, but especially instructional ones. Every step should have a picture, or even a short video clip if a still picture doesn't do the trick. The Vintage Singer Sewing Machine Blog is the perfect example of how to do tutorials in a blog format; everything is tagged in a group (wiring, restoration, etc.), and if a tutorial is part of a group there's links to the next post at the bottom.
I hope this helps!