You can get an adapter, make sure you get a stereo one though. I got mine from radio shack.

Laptop sound cards are usually not the greatest. If there is a "line in" rather than a "mic" use the "line in" instead. The mic in is made for vocal recognition and talking over the net and is not usually as high quality as the line in which is actually made for music. That may be the source of your hum right there.

As for repeats in cakewalk, I have 9, and use markers a lot. Once I have a section marked as the "chorus" it's easier to copy and paste that entire thing and see where it begins and ends. If you use markers, you can look at the marker view and see the structure of your entire piece.

My music was made in cakewalk 9.