Originally Posted by Salvato17:
Is it easy to install the 9 volt battery?
Yes, it's pretty easy. The instructions are on page 20 of your locomotive's manual. Just in case you don't have the manual at hand, here is the relevant page.
Edit: The manual page shown above is for the 6-11338 that you specified earlier. But this isn't a K4. Just to be sure that I've given you the right instructions, can you confirm exactly which locomotive that you have? The battery installation process should be the same though.