Not to call you out but that damage isn't a result of carry, that's shear neglect.
I'd guess it was stored for a prolonged
period in a poly bag or lying on foam in a gun box. (In a salt mine!)
If it were mine, I'd first get the gunsmith's OK in writing!
Next I'd strip the gun to single parts. Any internal part showing signs of wear or corrosion would be replaced.
All springs would be replaced along with any pivot pins regardless of wear/corrosion.
The barrel would get close scrutiny and need to pass my inspection before I send any lead down range!
I have a 6” grinder/wire wheel and an 8” dual buffer. I would take the wire wheel to both receiver and slide and wire off any rust. Go easy, watch the S/N
and Do NOT
create a lot of heat. Once the rust is gone, I’d start with a heavy grit compound and start buffing to remove the pits.
You are not going to remove all the pitting but you can make it a lot better. Just like collision repair, spray on this Lauer surface filler then sand and repeat:
DuraFil Surface Filler
Follow instructions and continue to fill until your arm falls off or you get it the way you like it.
Then finish up with Lauer DuraCoat Firearm Finish like this:
Lauer DuraCoat Finish
Jump in and don’t think about it. Just do it!