I picked up an extra door sill for some destructive testing.
After removing the "INFINITI" cover plate (plastic) which shattered into a million pieces you'll see this:

That is a "diffuser" panel, remove it and you see the source of the light:

Two little, VERY yellow SMD lights on each end of the housing:

You could grind away the edges to remove the cover (the diffuser and light boards just pop out) and then replace the SMD lights if you so desire.
Not really that hard -- curiosity just got the better of me today.

