There are many easy quilts that would be lovely and easy to make. I have several sites I go to on a regular basis. Here they are and the rest of us are available 24/7 to answer questions.
http://quilting.about.com/
http://www.ehow.com/how_2044939_make-quilt.html
Others on here will have more ideas on how to get started.
Oops, didn't answer your original question of how long. It depends on the pattern, the expertise and the skill of the seamstress.
What class are you taking?