What is the best way to remove the back 3 spark plugs?

Hello,

Replacing the rear plugs can be done using spark plug socket and an extension. There is no special trick to that, it is just little difficult to access.

Here is a helpful video that shows how it is done:

https://youtu.be/CE7bM8_j4Zg

Please let me know if you have any questions.
Thank you.