I opened up the instrument panel in my Nissan minivan a few years ago to fix a sticking tach, and that gave me access to (most) of the dash bulbs. Now a few have burned out and it's such a hassle to take the trim off and dig around, and worry about accidentally setting off the airbag, I haven't had the energy to go back in (I'm only so-so handy anyway). There was definitely a preferred sequence to follow in order to get the trim off for my van.
Try some of the links in the Online Repair Manuals discussion in the Edmunds Forums. Maybe one of them will tell you how to get to the cluster.
My guess is that your van uses simple wedge shaped bulbs that just push in, but you can always pull one and take it to the auto store and match it that way. Helps of course if you have another car to do the running around in. You might be able to figure out the part number by searching an online parts site like RockAuto too.