Yeah, it'll be hard. Right now I haven't worked out much more than the basic concept; I'd have a lot of writing to do, in addition to level design, learning RPG Maker, and so on.
As for art, RPG Maker does come with some built-in art and offers some more in expansion packs. If I have to, I can use placeholder art from the built-in assets and find some way to replace it once I'm happy with everything else.
Have you thought about how much time you are ready to put into the project? I'd ballpark the timescale for this as at least two years if you work on this alone, aren't becoming a full-time game developer and want to put a large-scale competent CRPG together.
EDIT: I'm guessing this would look like something like what Zeboyd Games puts out. They had a two-man team working full-time and took three months to make the short and simple Breath of Death. Didn't manage to find information on how long their more recent bigger games took to develop, but they seem to ...
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