1997 Buick Park Avenue gas gauge and engine temp. Gauge not

No need to take anything apart. Get a good magnet. (I used a magnet from a bad speaker.) Place it near the bad gauge needle. Move the magnet counter clockwise until the needle goes back to its normal position. It worked for me. My needle reversed itself so many times I got tired of it. I drilled a small hole in the dash glass a little past the full side of the gauge. I then glued a plastic rod through the glass to the gauge face plate. (I cut a plastic ball point pen insert and painted it black with a magic marker.) This ended the problem of the gauge indicator going past the full mark.