I just installed one
There are two cables from the pedal to up the back of the toilet one opens the water valve the other the flapper... My guess.. alas. though they are fairly easy to replace (I suspect) you will likely need to dismount the toilet to do it. Not a plesant job. I do not know if you can manually operate the valve from the rear.. I'd start by shutting off the water feed (I added a cut off valve and disconnecting the water.. Then remove the two base screws (7/16" wrench under the caps near the floor. then you may be able to turn the thing to look in the back without lifting it off the flange. Good luck.