I finally got the light apart. First had a heck of a time getting the housing to detach from the reflector/lens part after turning the plastic “screws” on the rear. Ending up using the edge of a screwdriver around the perimeter to finally break it loose. First thing I noticed was the rubber seal was pretty dried out, yet remained intact 
(btw, should it have a break in it, or contiguous circle? Mine had a break in it 
)
Once the reflector/lens was off, though, omg … the entire inside of the housing is covered with rust (so much for my belief that the housing = polished SS). What I can’t figure out is how any water got in there to do that damage, as tight as the reflector/lens was attached to it. It’s possible it’s repeated condensation, but if that was an issue with the fog lights you’d think Jag would have put a tiny drain/vent hole to the outside in the housing somewhere along the bottom edge. The outer translucent plastic “covering” on the pair of wires flaked right off when touched, exposing their (fiber?) insulation. I guess I’ll use the liquid electrical tape to re-coat them before final reassembly.
I then put the reflector/lens assembly in the oven, per the instructions from WelshNet. 350 degrees for 15-20 minutes. I admit I did leave it in there a bit longer than that, b/c my damn kitchen timer failed to go off. 
Taking it out when “done” I noticed the lens did not readily detach from the reflector part. Using my screwdriver around the perimeter though, it came off w/o too much effort. However, there was no sign of any gooey adhesive present. Instead, just a small part of the perimeter had a dried hardened substance on it that was kind of pinkish-white in color. It actually came off in one piece and could be broken into chunks. wth? Is that the OEM stuff that Jag used on them, or something done by a PO? Once I got the lens away from the reflector, I could see that in fact the orange coloration I saw from the outside of the lens was rust staining, due to the reflector being rusted up around the edges. Also, although there was no rust in the main center part of the reflector, it was a strange olive color. Only a couple of small patches of reflective silver were present on it.
Anyway, it looks like I will be using a lot of rust remover gel on all the inside parts, except the lens, to clean them up as best can. I’ll respray the reflector surface with some “silver” paint and I’ve already soaked the rubber seal in some WD-40 to help “revitalize” it. After that (and the liquid electrical tape job mentioned above), I’ll put it all back together with that white silicone adhesive sealant made by Dow as recommended by WelshNet. 
I’m just glad the other light is (apparently) in O.K. shape.
Oh, btw, the halogen bulb appears to still be O.K… However, after putting it in a baggie with the other parts it just came apart from its holder. So, I’ll have to get a new one. The electrical contacts on the “holder” also have rust on them, so I’ll hit those with a shot of electrical contact cleaner spray.
btw, I think I’ve gotten about all the rust off with the remover gel as possible, but there is now a large area that is black on the inside of the housing, almost like it had been hit with rust reformer instead. 
No idea why, unless the rust had eaten all the way through the chrome in that spot and that’s the color of the bare metal underneath. 
I guess I’ll hit it with some silver paint as well, if so.