That reg is perfectly fine for re-use. Those parts are in good shape, and the ONLY part that matters is the orifice (assuming that the diaphragm is also intact). If the knife edge of the orifice is smooth, it will mate with a new seat easily. If not, you can polish it with a pencil eraser or Micromesh ultrafine buffing pads. The rest of the parts aren't a factor, because the orifice holder doesn't move, so it doesn't matter as long as you can screw the orifice back in. The other part - the microadjust for cracking effort, is mated to a plastic piece, so it will adjust easily.
The only part that doesn't look ready to go is the piston for the microadjust. The shaft of that part is sealed with a small o-ring in a balance-chamber-like device, so I would polish the shaft until it's smoother. That's the one weak point of that particular Oceanic regulator design. It's also a bit of a hassle to reassemble, unless you do it frequently.
The second stage is much more forgiving of abuse and corrosion, since it's a medium pressure device with a replaceable seal. The first stage may be another matter, because the areas where o-rings seal may have to withstand 3000 psi.
