Just a little word of warning, before buying a flash programmer (plugs into your OBD port) you'll want to make sure of a couple of things.

1.  The seller has returned the vehicle to the stock setting.  If the car/truck isn't returned to stock the programmer will typically be VIN locked to that vehicle and will end up being useless to you.

2.  Contact the manufacturer and find out how much it'll be to have them release the VIN so you can use it.  Most companies make sure that if you sell your programmer that they still recieve a little more cash out of the deal.  From what i've seen, they average about $99 plus the cost of shipping.

Good luck, hope this helps someone.