what is the best way to get the middle piece off the trunk when clearing the tail lights?

Middle piece of the trunk? Not sure what you are talking about...the third brake light, the large piece of plastic between the two taillights?

yes that piece, between the tail lights

i think it has 3 - 10mm nuts and 2 clips or something close to that , you have to take down the carpet trim on the trunk lid and you need a deep socket. be careful with the clips , i got mine off and couldn't figure how to clear those orange pieces so i painted it black to match the car.

After you get the nuts off, the two clips are a bit of a bear to get off next. You need some good needle nose to close the two clip points closed so they can pass through the square hole on the trunk lid. You have to push those clips in while pulling the piece out. When you think you might break it, is the time they pop out.

Alright what does it mean to clear your tail lights?

It means to remove the amber colored inner plastic piece from your taillight assembly that covers your directional light. Then you have clear tail lights. However; most states still require you to have either a red or amber colored bulb for directional'*.

This might help.

https://www.gmforum.com/t278819/

Well what is the benefit of clearing them?

There is no benefit. This is a matter of personal preference and style.