Pontiac Repair: 95 Grand Am Help, blown fuse, gm dealership

Question
Hi, I just bought a used Pontiac Grand Am GT Sports coupe (3.1L V6) for $550. Going into it I know that it needs an alignment, but since I've been driving it I've noticed the reading for the gas tank fluctuate about a fourth of a tank. When I press down on the gas the gas reading goes down about 1/4th of a tank, and when i apply the brakes it goes back up. What could be causing this? Also the driver side power window does not go up or down, it occasionally makes a click when I press the button though. The passenger side power window does work however. Is the cause of this a blown fuse or does it need a whole new power window motor for the driver's side? Also what are some cheap, effective ways that I can increase the cars MPG, power and life/dependancy? The engine is running very strong despite the several kinks, and all parts besides the transmission are stock.

Answer
The gas tank either has a broken baffle inside or the tank was replaced with one without a baffle.
You either have a bad window motor or window switch.
To keep the car running good and clean, follow the factory suggested maintenance schedule for severe duty. Go to any GM dealership and ask them for the maintenance schedule.