If you already have the gaskets, you might as well pull it. I have a 98, and when I did the cleaning a few months ago, it was crud city. And I really did notice a difference after the cleaning; little more pep in the step. Yeah, the air passages are big enough not to be too affected by the buildup, but what amazed me was how clogged the egr passage and pcv tube were--that can't be good.
Plus, it's a pretty good learning experience to get in there and see what's going on.
Just take your time. Give yourself a Saturday *and* a Sunday. Take everything off the first day and scrub up those parts really good with a brass-bristle brush and several bottles of cleaner (Valvoline TB cleaner works *really* good). When you're all refreshed the next day, take your time and put everything back together carefully. Torque all the bolts on the UIM to spec, and you're all set.
