Using one of the free themes available on Posterous, Tumblr, etc. as a starting point can give you a good head start on looks and readability. I can't claim to have solved your other problems, but for embedding code, I've used Github gists, and added some CSS to my blog's template to make the gists fit in as much as possible. It took some manual work up front, but after that it's mostly a matter of copying and pasting the embed code for the gist. I'm using Posterous, for what it's worth.