after oil got in my firing chamber I melted two of the sparking end off my plugs what is the major engine damage

it cold be tulipping of valves, detonation of pistons in engine etc. best to find a small camera to look inside and do a compression test. it may have done pre ignition/detonation that can happen and burn a hole in piston as well as burn the sides of the pistons and damage the walls which would require an overhaul. but if you can find a camera that can go down plug hole lot easier than doing a teardown.