First, the D50 will work. For not much more, you could even get a D200 or 300.
Once you see the difference between a true macro and a zoom you'll understand more. The lens you mention is a manual focus lens. This is fine because most close up is better done with manual focus. On a zoom/macro, your magnification will be around 1:1:23 or something like that. With a true macro, the magnification will be 1:1. Your focusing distance will be shorter also. This will get the shot closer yet.
Once you see the difference between a true macro and a zoom you'll understand more. The lens you mention is a manual focus lens. This is fine because most close up is better done with manual focus. On a zoom/macro, your magnification will be around 1:1:23 or something like that. With a true macro, the magnification will be 1:1. Your focusing distance will be shorter also. This will get the shot closer yet.