S A Z will I need to download the base game before the mod or will it all be one package?
Yeah, you'll need to download the base game too I'm afraid. I intentionally don't include the base game because I have been around to see plenty of others run into issues with certain creators. They bring up issues with like missing traffic or people mistaking the creator of the Mod with the creator of the game itself. Now in most cases this just isn't an issue, but the headaches those rare case cause are just not worth it to me. So I err on the side of caution.
I do regular tests to make sure the Mod works on both the original and compressed version. There is rarely ever a reason for one not to work, but there is a difference that might get some people hung up. In the original version the majority of the coding and assets are stored in .rpa files. We can use UnRen to get the coding and assets unpacked and convert the coding to .rpy files. Once we're to that point you can move the files from the mod over into the "game" folder and overwrite the files needed and you're good to go. But in the compressed version you don't have to do this usually because the person that compressed it has already done that. So if you look into the "game" folder and there are already .rpy files in there and not .rpa files then you just need to move the mod files into the "game" folder and can skip the UnRen step.
There is also a little more you can do if you're running to issues. If after you've used UnRen and installed the mod, you still have .rpyc or .rpa files, you can delete those files, not only to save a bit of space, but because on rare occasions I've seen RenPy try to access those files instead of the .rpy files we want it to access, so there is that. Also if you are having issue even after uninstalling the game and trying again with a fresh install, try installing it into a different folder. That has fixed a few other's issues when nothing else seemed to work.
Anyway, I got off topic a bit. But yeah there you go.