I called Houston Door Pros on a Saturday morning. Mo answered the phone, I let him know I felt that my spring was the issue. He gave me the price range and what to expect over the phone and told me they would be out in a few hours.
James, the technician, was very nice, he talked me through what he was doing. When he was finished he told me that I should prepare to replace the opener motor soon because it was in bad shape. He didn't try to be pushy and get me to do it that day. Very Impressed!
When the power for your garage door is out and your car is stuck inside, you can usually still open your door manually. Look for a cord (usually with a red handle) dangling from the guide track that allows the opener to open and close the door. This is a manual override that you can use to open and close the door yourself.
Check if the transmitter on your garage's wall still works. If it does, it's likely that the transmitter in your car needs new batteries. You can usually do this easily. Just slide open the back of transmitter to remove the old battery and replace it with a new one. Some battery ports might need to be unscrewed first.
Most likely your photo eyes are the cause. Photo eyes are a safety feature that emit an invisible beam that prevents the door from closing if anything is in the beam's path. Over time, photo eyes can become dirty, misaligned, or need to be replaced altogether. Clean them (being careful not to scratch them) and re-align them with a level first to see if that solves the problem.
You might have broken torsion springs. Your garage door is very heavy and can not open without the help of a torsion spring. If you suspect a torsion spring is broken, have us check and make the repair; torsion springs are dangerous to work with and should only be handled by trained professionals.