gauges messed up

I recently purchased a 2006 f150 4x4 XTR . it had 69,000mi but some of the gauges started screwin up. the fuel gauge goes to pointing almost straight down when filled up and the oil pressure goes the same. they both stay the same but sometimes when i start truck the \both seem normal but not too often. the other issue is the odometer light dont work. any body know what bulb i need and any way to fix the other issues. Thanks

Go to Tascaparts.com and put in you VIN. That will give you the right bulb for your cluster. Had to replace the one in my '05. Can't remember the part number though but you'll find it on that site. And where do the needles on those gauge go when the truck is off? Back to where they should be (fuel on Empty and Oil Pressure on 0)?