You can change your plugs without removing the plenum, but it's tricky and requires having the right combination of plug socket & extensions. If I recall you have to remove a bracket or two but not the entire plenum. Try taking the covers of of the cam valleys and look at things before you start yamking the plenum off.

If you're still playing with it this weekend I might be able to give you a hand at some point. I've got my girls all weekend and typical stuff planned but I might be able to squeeze in a few hours of wrenching.

95 Montero SR
3.8 MIVEC, Advance headers, 2 1/2" exhaust, Magnaflow muffler, OME shocks & rear springs, 2" body lift, 3" tank lift, 4.90s, TRE front locker, factory rear locker, Roger Brown Rock Sliderz, 315/75r16 (35") tires, Sport big brakes