What is a fair used price for a used first generation MBA 1.6, 80GB HDD, etc. ? System is out of warranty over 6 months. What would you pay? Also, is it worth upgrading the HD to a SSD? how much should i expect to pay? my 15" MBP gets too heavy to carry around campus and the battery doesn't last. thinking of this as a second purchase. Should i wait for new models to be announced? your advice? thanks!