If you disengage the garage door opener and lift the door up by hand, is it an effort to lift it? If you let go of the door in mid-air, does it stay there? if not, then you probably need the springs re-tensioned.
I recently had my springs re-tensioned on my garage door which is quite large (14'x11.5') and heavy. The door wouldn't stay up on its own and I recently striped the drive gear in the opener (the gears are only plastic). I do not recommend re-tensioning the springs yourself, they can be quite dangerous! I would recommend getting someone out to look at that.
To check your alignment take a level and check to see if the door is level (horizontally along the top edge and vertically along the side). My door was out of alignment and needed to be brought back to true. The repairman fixed that in the process of re-tensioning the springs. The process looked simple, but if I would have done it on my own, without first seeing what he did, would have probably made things worse :-)
In addition to lubing the wheels and hinges, spray a light oil coating onto the springs themselves. I was told that rust forming on the springs causes friction and makes the automatic opener work harder then it should. This should be performed on a periodic basis probably twice a year to keep everything in good working order.