Go to the MTH Electric Trains website
http://www.mthtrains.com/content/product-locator
Select Service then select Product Files & Documents.
Type in the part number of the Challenger, and the available document files will come up.
Unfortunately, there is no documentation available for the 20-3000-1, but there is for the 20-3244-2:
http://www.mthtrains.com/sites...ction/20st18581i.pdf
I did not find a parts manual for the Premier Challenger.
Call MTH Service and inquire about a parts manual for your locomotive.