I wouldn't suggest doing that unless your headlights seal has already broken. Because you will not be able to seal them back once you open them. This is true with all aftermarket lights when you buy them (e.g projector headlights etc), with each wash or rain, the water will stay inside for weeks and it will all be messed up. If it is sealed, there is no way it has dust build up inside, and you are better off with just polishing the outer surface.
If you want to go an extra mile, you can first use 2000+ grit sand paper followed by machine polish and your lights will be crystal clear.
After that, simply apply any window sealant so that they don't oxidize as by polishing you will remove the protective layer over the lens, and its oxidizing chances will increase.
But all in all, i would suggest if your lights are never opened before from stock, don't open them unless they are broken or damaged.
PS: There is one way to clean them from inside but its a bit lengthy.