You should now be able to see the bulbs if you peer into the opening. The space was too limited for photos. Getting the bulbs out are quite a tough business, since there is not enough space to get a proper grip on the bulb - or maybe my hands/fingers are too big. I used a needle nose plier to grip the bulb on the metal part on one side and a small screwdriver to push the bulb holder jaw open on the opposite side.
I bought some long-life bulbs at Kragen (Picture 5), as it is a real PITA to get the bulb out and back again. The 6418LL is the correct size and rating. If you thought is was difficult to get the bulb out, you haven't yet tried to get the new one in.
The bulb fits VERY tight into the bulb jaws, presumably so that they don't pop out when you slam the lid. It took me about 20 minutes to get the first bulb in. When I had a look at the second bulb, I noticed that it wasn't seated properly, and it popped out when I tried to re-seat it (presumably last fitted at the dealer for the previous owner, since it was a replacement bulb!). So I fitted a new bulb there as well - which only took me 2 minutes! The trick is to fit the one end of the bulb into the hole on one of the jaws from BEHIND (furthest away from you). Then pull the bulb towards you against the other jaw with your finger while you push simultaneously with a small screwdriver against the jaw to open it up. It may sound complicated, but that is what worked for me.
Once you are done, reconnect any wires you may have disconnected or dislodged in your struggles. Test the lights to see if your job was good before you start to refit the liner.
To refit the liner, first start with the studs in the center of the trunk-lid. If you don't do these first, you will not be able to get these studs in after the ones on the edges have been fitted first. You may have to stretch the liner a bit to align the holes. Push the stud the whole way in, and then push the post in the hole. Now maneuver the liner over the rubber stops and trunk light switch and under the trunk lock and push in the remaining studs and posts.
All done and no more warning on the console.