The speedometer, tach, gas gauge and radio are all not working,

Look into a body control module

I would imagine all those circuits may be on the same fused circuit. Look at the fuses the fuse box is at the left side of the dash, open the door to axcess the fuse box cover. Look at fuse location and fuse ID in the owner's manual. Check here http://repairpal.com/automobile-owners-manuals-online or try this link you may be able to down load a free copy of the owner's manual for your vehicle http://www.autousermanual.com/