The plugs are not that hard to get out. Just don't get the wires mixed up. I still have little numbered tags on mine from when I did the head gaskets. Also, do not strip the threads in the heads when you replace the plugs. That will definitely put a crimp in your day.

 

When I did my O2 sensors, I sat up a walk-board using a 2 by 12 and two blocks. This allowed me to get high enough to quite easily see all the mounting bolts, plug numbers and such on the coil packs. Each point is numbered and make sure you know the numberingf arrangement of your engine. It is different than the older American
V-8's.
The plugs on the driver's side are 1-3-5-7. The pax side is 2-4-6-8-. If you look at the coil packs, each point has the number impression stamped. I remember someone who thought it was like a Chevy 350 and crossed up several wires. o excuse in my opinion.

I also use a swivel head ratchet and extension o certain plugs and a long speedhandle of others depending on the approach angle. KJeep the socket 90 degrees to the plug and use steady pressure.

Be sure and gap the new plugs correctly and I apply a dab of antiseize to the threads and start in by hand to avoid cross threading. Also ensures plug will come out freely next time. Others may object. Apply the silicone grease on the top and apply the boot.

 

if you do one wire at a time its real easy to keep them straight
im also a big fan of wobble extensions for stuff like this

 

Is it ok to use 7mm wires instead of 8mm? what would the difference be?

 

thinner insulation. im sure itll be fine and better than whatever old stuff youre removing. 8mm is mostly popular as thats the common aftermarket setup from places like magnecor