5.3 problem need help!!!

well i was going about 90 and i got off the free way and the truck kept turning off on me then it just started to knock loud all of a sudden
i took it out and apart i check the crankshaft that was my first guess but it looked fine and the cam was fine too it wasnt broken i checked if the vales were getting oil and the driver side was WAY darker than the passager side the driver side look like honey and they other was a little lighter than choclate
well they were not cloged so they were getting oil... i took out 3 spark plugs to move the crank easier and when i decieded to put everything back i looked at one spark plug and it was smashed and burnt
i allready dropped it in but dont know if just to get rid of it and get a 6.0 or it will be cheaper to fix it and i dont know what the problem is yet
its a 5.3L off of an 01