For the most part, it certainly looks original. But in the aviation world, and especially when trying to keep historic birds together, it is not uncommon to patch or replace only a sub-section of a larger panel. If you look closely, the panel on the bottom of the cowling, towards the leading edge is cleaner and smoother than the rest, which suggests replacement, possibly modern. Just to the rear of that panel is narrow band, with raised rivets, rather than countersunk, and the rivets are not uniformly spaced. To me, this suggests a quick field repair, perhaps during a period of active, heavy use.
No, they don't just swap in propellers frequently. Props for beasts like this are very few and far between, and I would be extremely surprised if new blades are available. Like most things on in the aviation world, those would be overhauled. Even an overhaul on such a prop would likely cost as much as a nice used car. There are few quicker ways of burning money than playing with warbirds.
Those are Hamilton-Standard, Hyrdromatic, dual-acting, constant speed propellers. What that means is the blades rotate around their primary axis in the hub, changing their pitch, regulated by a "governor", to keep the RPM of the engine constant, with aerodynamic load. The governor sends oil pressure to either side of a centrally located hydraulic piston, which continuously adjusts propellor pitch. The pilot can adjust the target RPM via a lever in the cockpit.
A bunch of words, but lets just say it keeps the engine operating in it's most efficient power band, and prevents an overspeed in a dive, or underspeeding on a climb. Really, very elegant pieces of purely mechanical engineering.
FWIW, I grew up in the general aviation community, and did 4 engineering co-op rotations at Hartzell Propellor in the late 80's.
