The time will eventually come when it comes to getting repairs done on the old garage door. Nothing lasts forever, especially these doors. Before trying to fix it yourself and risk messing it up, I think that it would be better to contact a local garage door repair service that can come out and do it for you - view http://www.allareaoverhead.com/garage-door-repair-austin/.
I would rather see these pros fix it than to have you struggle on something you don't know how to fix by yourself. After all, you could risk messing up the mechanism or possibly hurting yourself in the process. It is best to just avoid that altogether.
A team of professionals can easily come out, figure out the issue, give you a fair quote, and then either fix it right on the spot or schedule the soonest time in case they need to make a massive repair on it. Either way, they can handle it because that is what they are trained to do.
If there were ever an issue with my own garage door, I would not hesitate to contact these services. They know how to fix it, whereas I do not. They would also fix it so that I don't have to pay more later from trying to fix it myself.