One bit of advice I would offer about sending things back through the mail:
USE LOTS OF PADDING!!!
Last year when I moved back to the States from Japan, I noticed that most of the boxes I sent back looked a bit worse for the wear. HOWEVER, I had packaged all my fragile items in MASSIVE bundles of bubble wrap. It was totally worth the investment as not a single dish, teacup, or ridiculously cute character model broke.
Overkill with the bubble wrap will be your tomodachi!
As for cost, you may want to consider sending things back via surface (i.e. sea) mail. It does take longer to arrive, but can end up saving you hundreds of dollars, depending upon how much you are sending back, of course.