1988 Toyota 4runner gages

Check the gauge fuse.

Could be lots of things, you really need to take a repair manual with a good troubleshooting section (like the Toyota Factory Repair Manual for your specific car) with a complete and accurate wiring diagram (Ditto), basic hand tools and a test light & multimeter, and start tracing out the circuit.

It might require a few nasty physical contortions to take out the instrument cluster or crawl under the dashboard, but it shouldn't be too hard to fix technically. If NONE of the gauges are working, it points to a common power problem.

Off the top of my head: Blown gauge fuse, bad Accessory switching contact in Ignition Switch assembly, bad Accessory power switching relay in the fuse/relay cluster, bad gauge voltage regulator (usually on back of cluster, or built into one of the gauge movements), loose wiring connector on back of instrument cluster, bad ground from instrument cluster to chassis ground point on cab cowl, Bad ground from cab to battery (-) post...

Modern cars have gotten MUCH more complicated - I remember when you could draw the entire wiring diagram of a 1960's car on one piece of paper, from memory, and build & install a whole new engine/dashboard harness by hand in a weekend (Been there, Done that, '62 Dodge Dart) - you can NOT do that anymore.

Spend the dough for the Factory Repair Manual, and the supplement books you may need - it's going to run you a healthy chunk of change when you ask at the Parts Counter (I can see your jaw dropping already from here). But the first time that book totally saves your (butt) it has more than paid for itself.

Accurate information isn't expensive, it's priceless. ;-)

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And the connectors behind the inst. panel.

Absolutely! And also...