Why won't computer start after magsafe adapter mishap?

When I found that my computer wouldn't start, I removed the charger from the port (DC end) and the computer side of the port was brown, cracked and had what appeared to be magnetic debris lodged inside. There was also a pungent smell around the charger port. After I cleaned the port (no liquids) I plugged the adapter in and hit the power button, only to hear a sizzling noise! I'm wondering a) how something managed to get inside the port while the charger was plugged in, and b) how can I tell if this is just a blown fuse, or a fried computer, short of taking it apart. I've tried taking out the battery, using other chargers, resetting the SMC, PRAM, etc. I've cleaned it with compressed air and other safe methods. ALSO, the battery is fine, the indicator light flashed 4 bars.

This is a late 2007 MacBook that I've had since about that time.