How do you combine 2 or more tracks into one track
Using just iTunes, you could put the two tracks into a playlist, and then burn them to a CD. Next reimport the tracks from the CD using "Advanced > Join CD Tracks", and you'll have them in a single track.
how do you divide one track into multiple tracks?
Do a Get info on the track, and in the option tab, set the start and stop times for the section you want to extract. Now go back into your library screen, and use the "Convert to ..." command. That will create a new track with the start and stop time you set.
Rename the new track as you please. Now head into the Options tab for the original track. Reset the start and stop times for the next chunk you want to break out, then do another "Convert to ..." ... and so forth until you've got as many shorter tracks as you require from the initial track.