Speedometer not working

Needles moves when car is started then goes back to 0 mph, but does not move when driving and the odometer is not recording either. Recently that along with my car stereo stopped working after unplugging the wiring harnesses to hook up a JVC stereo which also did not work. The windshield wiper blades are now not working unless I cut the AC off as well as the power locks. I have no idea why this is happening except for maybe that when I disconnected the battery to make the engine light go off that maybe it caused some sort of short? Now the engine light is back on and I am having all of these problems. I am sure my husband and I can fix it we just need more of an idea on what and how to go about it. Thanks in advance!