If your Navy Arms rifle is the lever action Yellowboy (reproduction of the Winchester 1866) they list for $400-500, depending on condition. The carbine version has a slightly lower value.
100-300 dollars
.32 short used to be available from Navy Arms or try some of the local gunshows for the Navy Arms .32 short rimfire.
50-200 USD or so
20-300 usd
That is FAR too complex (and potentially dangerous) for a brief answer here. The link below will take you to an owner's manual for a Navy Arms in-line rifle.
Navy Arms produced the 1860 Henry rifle from 1973 to 1999. The company is known for its reproduction firearms, and the Henry rifle was one of its notable offerings. These reproductions were designed to capture the historical essence of the original Henry rifle, which was first produced in the 1860s.
50-475 usd
I am not familiar with a Navy Arms Country Boy rifle- but if by chance you have a Navy Arms Country HUNTER .50 caliber muzzleloader, they are pretty much a traditional muzzle loading rifle. Remove ramrod, draw back the hammer, tap the retaining wedge pins out of the stock, then lift barrel out of the stock. Right there is a good place to stop. You can check with Navy Arms customer service through their website to see if a manual is available for your rifle. Also check to see if this rifle uses a removable breechplug. Some black powder rifles have a non-removable breech plug.
50-300 USD or so
Navy Arms was an importer/retailer. Provide a DETAILED description of ALL markings.
50-200
$500, more or less, depending on condition.