Broken black water valve

Depends....First if the tank is empty. It will be as soon as you remove the valve! You will have to look at what is there. If all of the fittings are glued end to end with no room for a coupling where you need to cut the pipe, you will likely have to replace everything from the valve out. If you have roughly 5 inches of straight pipe attached to the valve, it will be a simple process.
The valve itself is 4 bolts and remove.
I basically had to replace everything from the valve out after a tire blowout. I took everything off as one piece and walked into my local, small town RV repair shop. We mocked up the replacement right on the counter. I then went home and installed and glued each piece just like the original.

Replacing the black tank valve on our Fuzion was not an easy job. The coroplast had to be removed and then put back in to place when done, that was the easy part. The valve was very hard to get to, and also very little room to remove it. Ended up having to loosen the sewer line in a couple places to allow room to remove the valve.

Definitely do-able, but not a 5-minute job by any stretch. None of them are exactly the same.

If you can get at the valve, it's pretty easy (assuming you remember to empty it first).

If you have to tear apart the underbelly to get at the valve, it can be a big project.

About 4 years ago I noticed a small crack in the grey tanks dump handle on our 24' Class C. It still worked but the coach was definitely giving me a warning/heads up. I went on line {Amazon } and ordered an entire new dump valve assembly {for both grey and black - if one is going bad rest assured the other will not be far behind} for about $100.

I was able to do the replacement at home with all of my tools vs stuck somewhere on the road if I was even lucky enough to be able to acquire the requisite parts. There was more reaching under the side of the coach vs crawling under It took about an hour and half
and was fairly easy to do, just reverse engineered the removal of the old valves.

Now picture reaching for that valve and having it break off in my hand at a crowded dump station... :S Order the parts and do it yourself or ask a buddy if you have one with more expertise than you. As noted above look for any RV repair shop to be backed up weeks/months and about three times the cost of doing it yourself.

Good luck.

:C

Search for "black tank valve replacement" on YouTube. You will see that it is a simple job IF you have good access.

The hardest part is crawling around under the RV....when you forget one tool or part.
RV repairs establishments will probably have a LOOOOONG wait list, even for something as simple as replacing a black tank valve.