Changed my 4.6L plugs (in my '00 Econoline) two weeks ago at 74,000 miles. The #5 coil went bad, so I while I was in there... - it took about 4 hours. I had to take the fuel rail loose to get plug #6 out, and left it off for 7 and 8. Knuckle scars are just about healed.

There's just a lot of hardware, hoses & wires to poke an extension through. My tip is to get different length extensions, and maybe some u-joints for your socket set. Plus, a 7mm socket and a 1/4" drive, or an adapter for your 3/8".

Or just be happy that YOU don't have to change the plugs on an Econoline.