You know, sliding glass doors that stick like this can certainly be annoying and sometimes even dangerous. Now oftentimes it's possible to correct a problem like this with a simple adjustment. You can remove many sliding aluminum doors by lifting them straight up. The top of the door will go into an aluminum channel in the top of the frame and the bottom will swing free of the track. Sometimes the solution is as simple as adjusting the bottom track wheel by turning the screw on the sides. These track wheels can wear out though. If that's the case, remove it, take the old wheel down to the home improvement center or hardware store, get an exact match and reinstall it.
Before replacing the door, I recommend lubricating the glide wheels, cleaning the bottom track and applying a coat of paste wax. Now once the door is back up, you may have to make some minor adjustments to those guide wheels, but after that, you'll have once again a sliding or even gliding glass door.