I agree that you probably have a broken band. That much you should be able to see fairly easily from the side plate.
As far as changing it... I think you can probably do that through the lift cover... but don't hold me to that.
IIRC, the band is pinned to the actuator lever with a hard pin and cotter key... so IF you can get access to it you should be able to open the band and change it. If you've got one that's riveted to the actuator... luck will not be on your side. Be good to get one in your hand and look at it before a split. Beyond that... if you have to slide it off the shaft, Bern is 100% correct. A rear split will be the easiest route to go. It can be done through the top by removing the rear top shaft but it's a BIG pain.