My experience with publishing is that you don't need to be glossy, but it does need to look professional, especially if it's a larger adventure. People are willing to drop a few dollars on a ten-page adventure that's not very fancy, but the larger it gets the more they want it to be a professional work. This is equally true on either Drivethru or on DM's Guild. Itch.io is much more forgiving of works that don't look professional, but usually Itch sales are just going to be enough to get the money together to turn a popular product into something more glossy.

In your case, a few public-domain images might be nice; careful text formatting is probably very important, and setting up some proper heading bookmarks and integrating the word and excel into a single well-constructed PDF would be a good plan. But I would say go for it!