Well, they've lasted since 2002, so they are pretty durable. I would say just polish what you have. Aluminum is so much better looking than wheel covers. More than that, you will be paying more than just $250 to get steel wheels and covers. you will have to mount your tires on the steel wheels, and then pay for balancing too.
As for the polishing process, I don't know if they have to de-mount them before they polish them.