Or, if you're like me and didn't get a manual with your truck I'll do you one better.
Straight from the manual:
You need to reset the light after the engine
oil replacement. Reset the light by
following the procedure below:
1. Turn the ignition key to the “ACC” or
“LOCK” position with the odometer
reading shown. (For details, see
“Odometer and two trip meters” on
page 144 in this Section.)
2. Turn the ignition key to the “ON” position
while holding down the trip meter
reset button.
Hold down the button until the light goes
off. Before the light goes off, it illuminates
for 3 seconds, flashes for 2 seconds and
illuminates for 1 second.
If the system fails to reset, the light will
remain flashing.