You might get away with just resealing the injector. Remove, replace all of the seals, including copper washer on the tip. Reinstall with proper fastener torque.
That looks like it still has the DPF as well. Probably some dumb California rule keeping it from being registered versus being deleted.
Then, it has a butt load more miles than the one he is looking at now.
I agree that one of the nuts that holds the piston to the ram is off. I'd unpin them both from the bucket and pull on each ram, one at a time. You'll find the problem.