You can drag songs over to the microSDHC card, but I don’t think playlists will recognize it anymore. You’ll have to make separate playlists for the microSDHC card.
It will certainly update the song info, but whether the album art gets copied over depends on what version you’re using, how the album art is stored, and how you copy it. Older versions (prior to the release a few weeks ago) didn’t recognize album art in the song, so you had to have an art file (usually folder.jpg) in the directory with the songs. To keep it from showing up under pictures, it had to be hidden. If you use Explorer to copy the entire directory, that art file will get copied over. If you just copy songs within a directory, by default a hidden file won’t show up and thus won’t get copied.