It looks like a brass framed replica of a Colt 1851 Navy. I have one that is a steel frame. As far as parts,it looks like you will need a wedge (it holds the barrel assembly to the frame of the pistol), and an entire loading lever assembly. Sources for parts would be , Dixie Gun Works, and VTI replica gun parts.
In the third picture you posted (good closeups BTW) the serial numbers on the barrel and the frame do not match. This means that the pistol is not how it came from the factory.
Brass framed pistols while looking very pretty, can tend to stretch the frame and "shoot loose" if they are used with standard to heavy powder charges. If you get this one working keep it light.
I was thinking of taking one of my c&b pistols to a smith awhile ago, and I wanted to find someone who pretty much specialized in these type of guns. It was suggested that I ask at my local cowboy action shooting club(SASS), or civil war reenactor club (NSSA).
Bottom line, if the frame is good you should have a nice c&b pistol. Have fun making smoke, and please use real black powder it's highly addictive!
Also be sure to read the "sticky" at the top of this forum, the one written by Gatofeo entitled "proper use of cap and ball revolver" all the basics are there.