Hey Christopher
Check your LCD's display connections. When you replaced them at least on this model they should click back into place. If you had ran the Mac when the cable wasn't correctly plugged in, you may have shorted the Logic Board. Apple has discontinued support on this model so if you need a new Logic Board you'll need to head to iFixit, or eBay
Check that there is not corrosion, or ashy looking colors on the copper connectors. If the Mac is making a buzzing/hissing noise DO NOT TURN IT ON!! This is never a good sign, usually this means an electrical issue and the Mac can begin to smoke and catch fire.
First before working on the Mac unplug the main power cable on the back of the Mac, and hold the power button for 10-15 seconds to drain any power that may be sitting inside the system. Then recheck every cable you had disconnected and check for abnormal connectors on your display.
Good Luck!