2001 Jeep Cherokee Not Starting

Side Note: Less than 1 year ago I had a new battery installed. The installer had to cut back connector wires as there was much corosion.

Currently when I turn the key I get a "tommy gun" type sound. Then after trying a couple of times I just get a click sound. Also my gas gauge had stopped working last winter and suddenly the gas light went on and the guage moved - it is not accurate - but it moved. At the same time the radio stopped working when the fan was turned on. Also the electric windows sometimes don't work.

I would like to have some idea what the problem may be before I take it anywhere to be fixed. I looked through the manual and the only part that seems applicable is the electrical power distribution center.

Any help or information is appreciated!