The 1st part of your question is a point of status. This is good. It gives a starting point. The 2nd part is an action. This is even better! I've never known a pawn shop to turn merchandise so quickly! :) The 3rd part is rather a question of money. If you leave some programs on your computer, it may be worth some more money. Ex: Office. It runs over 300 bucks to purchase at Best Buy. About backing up, I would definitely Not leave anything on your laptop that would lead a possible buyer to you. Go to Target, Wal-Mart, Office Depot, and yes Best Buy and get a WD back up for about 50 bucks. Plug it into one of your drives and it will categorize and copy all your emails and anything else you would like to save. Dump it into the little passport. Surprisingly, it des all fit! .
You can leave your downloaded programs in your laptop if you are pawning it. You can back up your email by using Lion's Mail Client, which allows you to select various emails for backup. An external drive can also be used for backup.