Cool - nab yourself a high capacity battery on ebay, a couple of Transcend 4GB SD flash cards on newegg, and a coax cable with a mini plug and you will be ready to rock. You can run optical in but the coax is more bomber and you'll have optical for backup or patchers.
Keep your JB3 and run a 16 bit truncated copy for backup, just in case, for a little while. Then, sell it when you are super comfortable with the PDA setup. With the right flash memory and the latest software it will be a lot easier than it used to be. Make sure you always format with at least 32KB clusters.