Just finished replacing the rear bank of spark plugs on my GXP.

Damage, 1 sacrificial 10mm 1/4" drive socket lost in the depths of the engine bay during the first attempt to remove the nuts off the air valve connection to the exhaust manifold. I had to resort to "duct taping" the socket to the extension shaft so I wouldn't lose another socket. Also used grease to retain the nuts in the socket during disassembly and assembly since this portion is a "feel" job where you can't actually see the nuts.

Other than that, it is a real tight fit for all components but the job is doable.

There is also a youtube video I found:

Cool... Im going to change mine when i get a free weekend soon.. But if not i'll get to it after it warms up outside.. lol

The OEM plugs feel like they are installed pretty tight. Once you break them loose, it feels like you'll strip the threads out of the heads (did mine with engine cold). Just work them out slowly.

BTW, I had to disconnect the connector from the coil harness to the #8 coil pack to gain enough room to clear the air tube bracket when removing the coil pack assembly. It does barely squeeze out between the firewall and the cylinder head.

I just changed mine in, front ones are a breeze, rear ones aren't that bad, once you get that valve out of the way!
The 2 short extension method was the easiest for doing the rear plugs, slide the plug socket and one extension in then attach the other extension, get them on the plug, attach the socket and crank away.
I did learn the hard way about installing the bottom nuts on the flange, drop one, grab another one and drop it too.
I found some more flanged nuts and then smartened up, wrapped the socket with the nut in it with a bit of tape and it worked out perfectly.
Made sure to use anti-sieze on the plug threads, whoever did them last didn't and I could feel it when I was removing the old plugs.
Seems too logical, if spark plugs are going to stay in the engine for around 100,000 miles then why take the chance, especially in aluminum!