If you're not familiar with the Remington New Model, I'd invest in a reproduction and learn about its internals, what parts do what and go where, etc. You can swap parts to see what fits, see what might have to be modified. You could learn to shoot the repro before shooting the original (again, if you don't already know how). And, you can always sell the repro.
I would soak the cylinder in automatic transmission fluid and acetone for a few days to try and loosen the nipples enough to remove them. If they don't come out you can have them drilled out or leave them alone if they're usable.
Is that a nickle finish?
New Model .44