We threw out the info that came with our new trek combination lock. now we have no idea how to open it or to reset it.

Try this....
My new lock didn't come with any instuctions. I followed the link above and located the "bike locks" heading. I found that the question:

- I have a Kryptonite resettable combination lock and can't find the instructions for resetting it. How can I change the combination?

contained a pdf titled :

- Resettable Combination Cable
(red reset buttons inside)

which is not the cryptoflex 1218 but is compatible anyway.

dont hurt your fingers trying to depress the nodules as the diagram says though. to my chagrin i discovered that they will turn easily if you just push them around into place.

here are the instructions:

To set your own combination
Your new lock is preset to open at 0-0-0-5 at the factory.
1. Open the lock by aligning the opening combination
number to the Guide Points and pull out the Lock
Post. (Figure 1)
2. Push down the two Reset Buttons simultaneously
with thumb and forefinger, and turn counterclockwise
until it comes to a stop. (Figure 2)
3.You are now ready to turn the dials to set your
secret combination, such as a phone number, birthday,
etc.
4. After setting your secret combination, turn the
two Reset Buttons again by Thumb and Forefinger
clockwise until it comes to a stop and back to its
original position.
5. Verify your new combination before using your
lock. Insert the Lock Post all the way into the Locking
Port but do not turn the dials. Pull out the Lock Post.
Your lock is ready to use.
6.The reset operation is now complete. Repeat
steps 1-5 anytime you wish to change your secret
combination.