I have only taken an intro graphics course, so my advice is more from a general computer knowledge viewpoint.
If you understand the basic concepts, and have a good foundation of what is happening at the base level, then learning any tool you use to accomplish what want to do will be reasonably easy with things like youtube videos, or a good book.
If you don't understand the basic concepts and will have to spend hours understanding things like basic texturing or what a b-spline curve is (or whatever is relevant in Maya modelling), then a course might be the best way.
Worst case, try the video/book method and if it doesn't work, take a course.
One thing to consider, although Autodesk software is crazy expensive (Maya is like $3500?) , you can get a 3 year license for free if you are registered as a student ( see
http://students.autodesk.com/ for details). I don't know the institution qualifications, but as a UofC student I had no issues. If the class you sign up for offers this benefit, then maybe it isn't as expensive as it might seem.
edit: They also have some videos on the autodesk site, but don't know how useful they would be.