1999 Lexus GS300 license plate lights

Not, easy!
The Bulb comes out from the inside of the Trunk

So, you need to remove the Truck lid inside panel (See Video), reach up behind where the light attaches on the trunk lid, twist the Bulb socket out a 1/4 turn same direction ya unscrew a Jar lid and the Bulb pulls straight out (do not turn the bulb in the socket). Installation is reverse of what I just wrote.
See you tube video;
https://www.youtube.com/watch?v=R7vdo_YsARA

I was wondering if this was a trick question.

If you don't see little screws holding the light cover on, you will have to access them from inside the trunk.

remove/replace.

raise trunk lid look on the inside behind your license plate light there should be access to the bulb there. You will see the wires going in to the bulb there will either be a flt plate that can be removed to access bulb or where the wires enter there will be a round socket that you can twist counter clockwise and remove the bulb socket for bulb replacement. hope this helps.

Did you try with the key? The keyhole is in the top left corner in the trunk by license plate (opposite to the camera lens).
Also, make sure the valet button in the glove compartment is released (or pressed)

The license plate lights are accessed by unscrewing the lens. The backup lightbulbs are accessed with the trunk lid open, behind the cover.

Open the deck lid (trunk) to better access the lights. There will be 2 of them. Recommend replacing both at the same time even if only one has failed. Generally sold in pairs anyway.

Directly above the license plate will be mounted 2 clear light covers. On the right side of each light cover you can see a small plastic rivet. Push in the center 1/4 inch with a small screwdriver then you will be able to pry out and remove the rivet without damaging it. This will save you from buying replacement plastic rivets for re-installation. Remove the light cover with the bulb harness attached.

The bulb harness requires a short turn counter clockwise to remove it from the light cover and the new bulbs snap into the harness. No twisting or screwing. Replace the bulb harness the same way and fasten the light cover back into place using the plastic rivet.

Saves time because both bulbs and light covers are exactly the same style, there is no left or right. Cheers!

this is straight out of the book ok

1. Open the rear compartment lid.
2. Remove the rear compartment lid trim.
3. Pull back on the rear compartment trim panel.
4. Unplug the lamp connector from the rear compartment lid wiring harness.
5. Press the grommet out of the rear compartment lid.
6. Remove the nuts retaining the lamp assembly to the rear compartment lid.
7. Remove the bulb.

I'm guessing you are referring to the license plate light. There are two bulbs. Pretty rare for both to go out at the same time. It could be the fuse. You can check if the fuse location by looking at your owners manual.

I think the license plate bulb is W5W LL. (Check to make sure). You can find the bulb a your local auto store, Walmart, Target, etc....

open trunk,

remove felt liner from rear of trunk, (liner directly behind rear lights in side trunk) should be 4 plastic Phillips head screws. Loosing screws, then slowly peel liner away. You will see 3 nuts on each side, removing these nuts will loosing the rear light lenses, so you can pull the lense away from the body from the out side to gain access to the license plate bulbs. Re-install in reverse order. While in there I would recommend replacing your brake light and reverse light bulb. Hey your already in there might as well do a little preventive maintance.

you should be able to get to thru the trunk