You can post some details here, such as: the sounds, if the door moves at all, etc.
I just fix my 10 years old Craftsman GDO, since the plastic drive-gear tored-out. I bought a repair kit from Sears for $33, plus 2 hours of research in the Internet and 3-4 hours of actual work. Its not very hard, if you can find the right information and be patient to work for a couple of hours.