[Skytrooper]

I have installed and serviced hundreds of these doors. They are a ***** to change the spring. They are a lot of labor and manhours. The biggest issue is if the company that manufactured the door is still in business. Then at least you can find out what spring is inside, prior to removing the spring side end plate on the barrel. Some spring plates are welded on, some use split roll pins. At lift is necessary due to the weight of the barrel assembly. The slats will remain in the guides (tracks) during the repair. The door will be totally useless during the repair.
This is a very time consuming job. Do not expect to use the door for at least a day, possibly longer. If they cannot find the spring information, then the door will be unusable for however long it takes to Open the barrel and get the spring information….and then wait for the spring to get shipped. Rolling steel doors are no joke. $4500 for the job ? I doubt you can find it repaired properly for less. Good luck !