Your opening is correct for a 48" door, if this is a pocket door you are describing. Run a tape measure completely back to the end of the pocket and extend it to where the door stops. It should be about 96 to 98". In order to remove and replace the door, one side of your header trim must be removed. Look up and see if there are screws holding one side of the trim in place. If so, removing the screws will allow the trim to come down and give you access to the door.
You will be limited to the style of trolleys based on the type of track you have. I find that a three wheel trolley to be more stable. The trolleys, once released from the door can be removed through an opening at the end of the track. Removing the door usually only requires the release of a lock mechanism on top of the door, which you will only gain with the trim removed.
You can post pictures of what you see so we can see if you want to.
You will be limited to the style of trolleys based on the type of track you have. I find that a three wheel trolley to be more stable. The trolleys, once released from the door can be removed through an opening at the end of the track. Removing the door usually only requires the release of a lock mechanism on top of the door, which you will only gain with the trim removed.
You can post pictures of what you see so we can see if you want to.
