Do a search for headlight cleaner. There are several plastic cleaners or polish that will get the yellow off and clear them up. Then wax them and you won't have to do it for a while. As far as the center light, they are available for $50 or so or can be replaced with a 97 grille, or an after market one.
The side lights can be purchased off ebay or from here. Put a wanted add in the Parts wanted section and someone will respond if they have a set.
Good luck and scan the How-To Documents. The headlights are easy to replace if you get to that point. There are some tricks, so if you are not sure how to do it, post a question and someone will help you with the steps to take. It is not as bad as you might think. You just need to know the tricks.