Your local auto parts store should have a kit available to restore the clear plastic lenses over your headlamps.
To clean the inside headlight lens on a ford ranger just simply remove the cap and clean.
Yes
There are a number of Headlight cleaning kits available, some work, some don't. Google Clean your headlight lens, and call or research the companies to find the best.
it's a bad headlight, the seal is broken on the lens.
The same way you clean the outside. Tip: Remove the headlight first to get access to the inside. Pretty simple, should only take 2 or 3 beers.
It's called clearview headlight restorer and it's found at Advance Auto Parts
Plastic headlight covers need to be buffed with rubbing compound used to restore paint
Sell it!
That is doubtful. The contacts are probably burned/damaged.
Yes they sell restoration kits for headlights
The answer to how to clean your headlight lens depends on how dirty your lens is. If it just has bug juice and road grime any good car soap will clean it, just be carefull not to scratch the plastic. However if your lens is really yellowed or the clear coat cracked then you will need kit designed to clean the lens.
My Beetle is a 2002 it had some bad yellowing of the headlights, I tried The Headlight Solution at headlightsolution.net , the advanced headlight restoration kit worked great, it was fast, and easy. Good Luck.