I think you're not getting a response because it's not talked about much here.

IMHO, wings/spoilers are for speed which the Montero isn't exactly known for unless you're actually racing one.

Also, I'm not sure if aftermarket wings are even available for them here in N. America.

If I were to do something like this, I'd either find & use that elusive OE connector that may be there, or wire the light/LED's via a splice into your lighting harness.

As far as weatherproofing it, once you drill your hole for the wires, 1st repaint them (so they don't rust) and once you've finished running the wire through them seal the hole up using a good all weather, RTV type sealer. You can probably find this at a decent hardware/autoparts store.

Oh, be sure to use a grommet or some other kind of added protection to prevent the wire from rubbing against the metal lip of your newly drilled out hole.

HTH.