I think you'll be safe if you simply open mirror accounts on IJ and GJ. The reason for two is simply that GJ is known to have server issues and goes down frequently. No biggie, just make sure you have IJ as a backup. (erm, these are Insanejournal and GreatestJournal, respectively.) Then, use LJSec and LJArchive to quickly transfer your entire lj to both alternate journals as well as your harddrive (for comments/feedback, etc) and you're set!