Sucks that you lost yer key dude! One of my fears
I do believe that you need two transponder keys to program one yourself, so it looks like a trip to the dealer for you. People are posting that you can do it yourself with one key, but my manual says no. I don't know I've never had to try it.
If you are interested, this guy is selling transponder keys on ebay.
check it out here.
My Manual say this:
" You can program new keys to the system if you have two valid keys by doing the following:
1. Insert the first valid key into the ignition and turn the ignition on for at least 3 seconds but no longer than 15 seconds.
Turn the ignition off and remove the first key.
2. Insert second valid key and switch the ignition on within 15 seconds. After 10 seconds a chime will sound and the Theft Alarm Light will begin to flash.
Turn the ignition off and remove the second key.
3. Insert the blank Sentry Key into the ignition and switch the ignition on within 60 seconds. After 10 seconds a single chime will sound The Theft Alarm Light willstop flashing, and turn on for 3 seconds; then turn off.
The new Sentry Key has been programmed. Repeat this process to program up to a total of 8 keys."