Re: A project I have in mind...(but I need a little help)
That's a great vision, but rest assured, it will both more difficult and more expensive than you think.
The closer you try to get to duplicating that Marsh, the more difficult and expensive it will be. Build something that kind of looks like it would be easier and cheaper. For instance, the frame. That's not a frame you can just buy ready to roll. It's not even a "drop loop" frame as some are now reproducing for upwards of $900 (bare frame), but rather, a frame that bolts to the front and rear of the engine with no lower loop, the engine block being integral to the frame. To get it right, that would mean a custom motor block along with a custom frame. The $$ part would get ugly real quick.
First time bike - you might want to try something simpler that looks like the Marsh but is not a reproduction. Even that would mean a custom fuel tank and truss fork, etc.
Not trying to throw water on your fire, just saying it can be a lot more involved than you first think, so price everything out, see what you can find in the way of components, consider what will have to be custom made and go from there.
Best of luck with it.