New Gauges?

Potential wiring problems are very hard to diagnose in person, much less to guess at online. In general I'd suggest you get a multimeter and a good manual and check resistances and voltages for the gauge circuits in question. Check all of your engine and body grounds for corrosion. Check any pertinent fuses and the general condition of your wiring (nothing like an old car with a hacked in stereo and remote start system to mess things up!). If you suspect your gauge cluster (it's possible), consider picking up one at a scrap-yard and swap it in to see if you get the same results.

I had an old 3.8 years ago. It eventually had a bad head-gasket, and I made the mistake of trying b-sealer before breaking down and fixing it properly. This thoroughly clogged my radiator, so I always, and legitimately, ran hot. That may be somewhere in your car's distant past too -- or perhaps a bunch of radiator sealing 'quick fix' by the previous owner before changing a leaking water pump. Start with making sure all the air is out of your cooling system, and see if running the heat on full-blast brings down the temp at all. If so, I'd start to suspect a clogged radiator.

The oil pressure is just an on / off gauge. Check wiring to the pressure sender, replace sender if necessary.

The fuel gauge could also be a bad sending unit or wiring. You can jump the sender wires (at the rear of the gas tank) to see if you can get the gauge to move.

Good luck.