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Since you are dealing with plastic, any type of plastic polish for convertable tops like the one sold by Meguires will work. I have also had a lot of success with using just straight cleaner wax like the car cleaner wax in the maroon bottle sold by Meguires. This has some polishing elements plus the added protection of wax. Either will do a nice job. Be careful to not get the wax on any other surrounding dark plastic pieces as it will leave a residue or white film. Also, use a solf microfiber cloth or a soft damp tissue to apply the wax. This will lessen the likelyhood of adding more scratches to the plastic. Once the product sets up in a minute or two, wipe gently with a clean microfiber towel or solf cloth. Good luck with it.
I put a ton of miles on my '99 before I gave it to my son and not once did I ever have this problem. Could this be a contaminate on the inside of the lens as far as the fogging is concerned? If so, pull the cluster, remove the lens and a simple wipe would do it. The scratches would have to be handled as suggested above.