I am unsure if this has been pimped before, but the lovely sherlock has two brilliant posts regarding how to move your journals and communities to IJ. Post 1 Post Two
Remember that LJ backup tools are not just for migrating over to IJ. You should back up your LJ with these tools daily. I wish I'd realized that before LJ suspended me. Reconstructing the journal at IJ by hand was no fun :-)
clayboy