My recommendation is do a clean re-install of the used PB's OS, just to keep everything running smoothly. Then you should get a prompt from a Download Wizard, so to speak, if you want to copy items over from a different Mac. Let the machine do all the work, then repair permissions and get rid of what you don't want.
It's a little extra work, but better in the long run.
Also,if you have .Mac, you can sync your Mail.app with the web version and over to the new older PB.