Ed: I never had to do it, but the guy that purchased the boat did do it and I think that it took two of them 2-3 hrs. You need someone that is NOT too large to get into that locker.
I would think that some of that lube that electricians use to pull wire would be good to slop onto the hose to run it through the bulkhead/stringer.
It is not impossible, but can be a daunting task. Just getting the exhaust hose off the elbow can be bad.
The muffler on the H'31 is a fiberglass box that allows the exhaust hose to connect on the top of the box. You want to be careful not to damage that connection too. I assume that it is not as difficult to remove as the one on the elbow (less heat).