You can remove scratches by gently rubbing them with a cloth. Douse the gun with plenty of oil.
An all-steel Commander in .38 Super should be a sweet shooter... don't let it go.
Changes? The only thing I would consider changing on it are the sights, which aren't exactly ideal. The problem is that the front is staked in place, so changing it isn't a DIY job. Maybe a longer trigger would be a good idea, if you have big hands, but give it a try as-is first.
To consider changing anything else on this pistol, you need to consult John, our forum owner, who is the undisputed owner of ALL Colt Combat Commanders (at least all the blued ones). You're only looking after this pistol for him, so you need to run any changes past him first!
Too many people miss the silver lining because they're expecting gold.