Follow what Paul says and you won't go far wrong.

Just be sure that you have the right tools for the job though, and don't just go hacking away blindly.

The nasty overhanging Nikasil on the ports is a good area to start. Just cleaning that up can net you a couple of ponies. You don't even have to cut any aluminum to get good results.

If you've got the cases open then just look at the jagged lumps and sharp corners. They're crying out to be cleaned up. Nice radii is what you're after, not sharp corners.