Getting to the 454's rear lights is really simple and changing the bulbs are really simple, even more than the 450.
Tools needed: Crosshead screwdriver
Open the boot and locate the two screws on the cover. Undo these with the screwdriver.
Pull the cluster away from the car. This may require a firm tug on the outer edge, there is a pair of plastic tangs and a metal pin in a locating hole in the top. After doing this, you can optionally undo the electrical connector.
You may find that behind the cluster is mucky. I'd clean it before reinstallation.
Undo the 8x plastic clips which hold the bulb cluster in. These are quite thin and fragile so be careful here.
When you pull the holder away, there is a rubber gasket that needs relocating in a groove in the holder. Relocate it in there with the grooved edge up.
Replace the bulbs you need to replace. For the rear tail/brake, push in and turn a little for the bulb to pop out.
Once done, replace the bulb holder in the cover and reinstall on the car. When doing so, I found it easier to locate the top pin in the hole first and the rest should locate. Replace the screws and test.