I agree the owner should be responsible for the repair. But if for some reason you wind up having to do the fix then it is pretty straightforward. I would replace ALL cables while you are at it. Place cinder blocks on the floor under each cable and lower door until cables are slack. Replace one at a time and adjust tension evenly.
RV6 completed 1991 sold.
RV7 #72018 N767T first flight 11/21/2017 150+ hrs.
IO-360M1B MT 3 blade, Dual AFS 5600.
1941 J3 Cub
2018 dues paid.