This....
https://www.lowes.com/pd/Kobalt-7-Piece-3-8-in-Drive-Hex-Driver-Socket-Set/3387798
...may help. it allows you to angle the head a bit and get your 3/8" drive on for more leverage.
I did my plugs and O-rings a few months ago. It wasn't too bad but I do remember the forward most coil packs requiring me to hold my mouth just right!