Well, this may not be a good one as I have found that it is often NOT easy!
But I've never tried on your Rv model, so hope for better?
There are some things that I might suggest to look over and see how it fits for you.
The drawings for the plumbing on your RV are here:
You may want to do a look at the full drawings but I have done a small snip of what I might first try.
Click this snip to get a better view?
My first thought is that it may not actually be freeze damage but one of those things that happen at the right time to make us think that???
Reason I say that is the idea that water will be in the bottomof the tank if it freezes and that will tend to leak pretty quick if we add water but also will be down low, not coming from more on top of the tank. Something to try to get a better idea of where and when it leaks, perhaps.
But if the leak is coming from higher, not the tank bottom, there are several points on this snip where I might think to look first as they are drain pipes which fit into the tank top, often using a rubber type gasket. If that gasket gets degraded over time and then gets bumped, it may start leaking and need to be replaced. That gasket is shown as G-1 on page 2 of the drawings.
Maybe some testing will tell you if it leaks when using the sink versus using the vanity will help to narrow the search but then looking around the suspect plumbing, you may find a section of floor like under the vanity which can be lifted to get a small amount of access on the pipe???
But at the same time, it might be that they failed to get anti freeze into the shower trap and that might have frozen and make it look likea leak at the tank top as it runs around in some crazy fashion to finally drip out away from the actual leak??
Best of luck to you!