Absolutely.....this has been a big concern for us as we want to travel next year.Right now we have a small portpoti installed.
The first thing I did was to get into the engine room as far forward as you can, and check out the space along the keel. Just forward of that bulkhead, you will find the holding tank. I had to cut an opening to be able to take the hoses off and pull it out through the engine room. It wasn't that difficult to do.
I also took all the hoses out as they were original and not made for sanitation. I treated myself to a new electric head while I was doing this work. You may want to consider this because:
1) An electric head has a mascerator that grinds the waste which can much easier push liquid waste to the holding tank or discharge liquefied waste overboard.
2) The pump can push the liquid to a larger holding tank that you may want to consider, given the waterway regulations. A larger holding tank could go elsewhere too; not just the same location!
After removing everything, I painted in there.
So, from the factory, you have the head sending waste to a "Y" valve that goes overboard through a thru-hull or when turned in the other direction, sends waste to the holding tank.
First thing you should do is get the old tank in your sights and see what kind of bulkhead cutting (if any) you need to get the tank out. Next, remove the old hose from the "Y" valve to the holding tank. Take everything out through the engine room, wrapping the old parts in garbage bags.
Clean and paint it with cheap Tremclad Rust Paint, not expensive bilge paint or cheap house paint from Home Depot. Just good old Tremclad oil based rust-o-lium paint. Get a gallon of light grey (or pink if you want to be different).
With everything painted, the sewage smell will be gone and you can now feel compelled to paint the rest of the engine room. Some day... not now.
Ok, the other reason to paint is... now you can see what you have. If you can find a teenager, get them to crawl into the hatch under your V-berth bunk. That is a second location you could now use to put a much larger holding tank.
I sail on the open ocean and we do not have holding tank pump out stations along the coast. Really weird, but true. Therefore I just found a polypropylene tank that would fit back in the space where the original metal holding tank lived. It is about the same size, but you are not restricted to using the same as the original.
Let's stop here. It is late and my pictures of the holding tank to the deck pumpout fitting are not great. For now, your homework is to decide if you want to stay original OR get a bigger holding tank in the large wasted space under the V-berth so you aren't pumping too frequently. Remember, your new electric head has a macerator that can push liquefied waste that far!
Next, I'll send pictures and explain how you have a second factory-installed macerator pump on the holding tank that can empty the holding tank (in legal areas) overboard or have a pump-out site suck the waste out of the holding tank.
Good luck. We also have Zoom or cell phones for questions or concerns. I feel badly that you have waited so long to get this resolved. Don't be scared, you can't do anything too wrong that can't be easily corrected. I certainly hook things up backwards more often than not! At least someone earlier warned you to empty the tank first. Yea, don't ask me. Of course I was smart enough to do that. Sure. Sure I was.
The smell will be gone soon! I promise.