I realize this sounds a bit sketchy, but our nanny's dad has his own garage door business. He just replaced two doors for us and added a spring to another door, all for a VERY reasonable price. He did all the work by himself and start to finish was done in ~ 5 hours.
His business is Mobil Garage Door. Number is (832) 419-1293. The number forwards to her phone as she handles all the quotes/schedules/etc. for him.