
As with most cars, the rocker cover will look worse for wear after 20 years! However it's not expensive to bring it back to life and it will look great.
When I picked up my Brock Fairlane the rocker cover looked like this:
Taking the cover off just involves undoing the 4 nuts on the top. You will need a new gasket though probably for when you put it back on. You will need to take out the PCV Valve before you do anything else. The valve is pretty easy to get hold of but the grommet (which doesn't come with the valve) is actually discontinued so eBay will be your friend here! (I bought two just to be sure)
Next I had the cover cleaned in a chemical bath - just because I had one available but you don't really need to.
So now you're ready for the fun stuff. Head to your local sand blaster and talk to them nicely

Now that it looks amazing, time to get some shine! Use a fine flap disc on your angle grinder to get pretty close then grab a block of hard wood (jarrah or the like) and wrap some fairly rough wet and dry around it. Back in the day your cover would have just been put on a big belt sander so the sanding lines would have been going up and down it. So, do the same thing with your block of wood and sand paper.
Finally, you are left with a rocker cover which looks as good as the day it rolled out of the factory!
Total cost: $30