The valve reliefs on some engines are deep enough to make them non-interference. The Pathfinder VG33 is not one of those engines. The valve reliefs and the small cam profile mean the valves don't spend much time in harm's way, so your chances of a piston meeting a valve when the belt fails are lower than they could be with some other interference engines. I've read a few accounts on here of people getting lucky and getting away with just replacing the belt. (Keep in mind though that this definition of "lucky" still has you stranded until you can get it fixed.) If you don't get lucky, and a valve does meet a piston, the valve bends and doesn't seal anymore. When you replace the belt, you'll have no compression in that cylinder. Replacing valves means removing one or both cylinder heads (depending on how many valves are damaged).
I got my '93 without a service history and replaced the timing belt myself (using the service manual and this writeup) before I started driving it. If its prior belt changes were done at the recommended service intervals, the one I removed probably had another 10k miles left in it, and it looked okay when I removed it. But I'd much rather do a (comparatively) small job on my schedule and have it over with than have it crap out without warning at a time/place of its choosing, get it towed, and then have to tear it down to a short block to repair it.