I have the same question about my '96 XJS - there are slides on the top and bottom of the lights - I am pretty sure I can get them off but I am not so sure about getting them back on.
i've had some experience with this issue. there are reconditoning kits for headlight lenses. ge kit uses several grades of abrasive and a drill (not good) sylvania makes a great kit.
there is a cleaner that strips the uv coating from the lens, nasty brown stuff drips from the lenses, it looks clear at the end of the first step, then you use 3 different abrasives, by hand, to remove surface scratches. a few more cleaners, then a crystal clear uv sealer.
the hardest part is masking the paint and chrome. i was not as concerned when doing this on our windstar vans, as i am with the jag
long story short, it took a little over an hour, the lenses look like new. it has been almost a year since i did the first vehicle and it still looks like new. not bad for a $20. kit