The oil pressure sending gauge or the wires leading to it are known to have problems and the oil gauge will go to the end of the scale. This is not a real problem but is a pretty simple fix.
If the temp gauge is quickly rising and falling, you need to service the cooling
The cooling system is just that, a system, which depends on proper function from each of its component parts to keep the engine cool. Service the cooling system and replace any under performing or suspected weak parts. Any component part of the cooling system that is not fully doing its job will stress the others and your cooling system will overheat.
-Use a flushing/cleaning solution and then drain and fill the radiator with a fresh 50/50 coolant and water mix.
-Replace the thermostat with a STANT brand 195*.
-Replace the radiator cap. An old worn out cap will allow boil overs as the coolant flashes to steam. You will see the coolant temps suddenly jump from 210* to the Red Zone if your radiator cap is weak.
-Inspect or replace the mechanical fan clutch. A worn clutch will allow temperature creep at stoplights and in heavy traffic. Looking OK and working OK is not the same thing.
-Inspect the electric cooling fan. Apply 12 volts and make sure it runs. Confirm that the e-fan starts when engine temps reach 215-218*. Repair or replace as needed.
-Inspect or replace the coolant temperature sensor that activates the e-fan.
-Replace the water pump. The pumping fins can deteriorate over time and the pump will not flow enough coolant to keep the temps under control.
-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside.
-Inspect/replace the radiator hoses. Make sure the coiled wire is installed in the lower hose.
Read more about cooling systems here - http://www.offroaders.com/tech/engine-overheating.htm