2001 Ford Expedition stupid mistakes most commonly made by

Soooooooo. I kinda forgot to change and check my oil all year. Im sure yal know where this is going. Im driving along and outta no where I hear a knocking sound from my truck as I passed under a bridge (gotta love an echo) well I go to a gas station and check the oil. I was low so I put 3 quarts of 5 w30 supposed to take 5 w20 but oil is oil when you kind of dont have a choice. Knocking is still there. Not a tick and sounds to be from the bottom of the engine. Upon starting it knocks and stops at idle. Ticks at idle. Accelorating it knocks but once reached a steady speed it slows when the rpm sattles to under 2000. Soooo bent rods? Piston severed? Rockers? Anybody know what this irresponsible idiot I am decided to break on a truck im having a hell of a time affording as is. With x-mas coming up I cant afford a mechanic to fix this. But I just hope I might be able to afford the parts to do it my self. I have never taken apart an engine b4 in my life but I never changed rear gears b4 either and I managed just fine with out any advise. Just gotta know what im looking at here, im just hoping I didnt bend the crank shaft