How do I protect and market my code?

Basically I had a over the summer assignment which I used to develop a piece of software which I guess will sell around 50 - 70 bucks a copy.

To make this clear. The final code is in Java (a requirement).

Now I was think about marketing my little creation however I'm faced with two problem:

1, I need to provide full documentation to the Lecturers. How do I go about preventing them from stealing my code/methodologies used? Would simple copyright be enough?

2. How do I bundle the software? How do I sell it? Should I partner with a publisher or should I just sell the code to a software company? I will need bi-yearly maintenance at least.
How do I protect said software from getting cracked?

How /prog/ has some experience on this already!
Thanks for helping out!

Was this a summer assignment for university?

You may find that the university will hold copyright on any work done for assignments, or possibly for work done on university machines. You'll want to check your course introduction pack etc. I know there was a something like this at my alma mater