Passenger side is 1,3,5 bumper-to-cab, and drivers side is 2,4,6, no other perspective, it should be the #6, unless he has a right side drive truck.

The over the fender kits do work, i fixed a spark plug on my Dad's 22r that way, and it held until the head was replaced.  How permanent it is, I don't know, but it would be worth the money to try.

I would unbolt the t-case from the X-member and tilt the engine forward, to give you a little more room to reach the #6 plug. 

Helpful hint for installing plugs: 
Install the spark plugs using a small section of rubber hose, instead of a socket on an extension.  If the spark plug starts to x-threads the hose will slip on the plug, whereas the socket and extension wont.  Also torque them to 13ft lbs, not hand tight, over tightening them is an easy way to screw up the aluminum threads.