when disassembling the cylinder from the engine try to remove any dirt/mud/oily crap round it so it dose not end up in the assembly so you don't end up having to meticulously the internal parts. the head gasket is re useable if you anneal it or use "copper form-o-gasket" on both sides of the gasket. the base gasket is made of a card Bord like material and will need to be replaced so you will have to order a new one or buy gasket paper at an auto parts store and make your own gasket. while you are at it inspect for excessive carbon build up in the exhaust port. the carbon build up reduces flow and makes the ped slow, it can be removed by solvents or by scraping it with a flat blade screw driver. further more inspect the cylinder head for carbon, remove the carbon with dish washing powder and a green scrubbing pad, if it is really thick carbon i use sand paper but some people don't recommend it. if you know how to remove piston rings from the piston with out braking them you should do so and see if they have developed thin spots. thin spots usually occur opposite to the side of the ring gap and or around where it would come into contact with the exhaust port. thin spots are bad, they are the point where the ring would snap in half in the future. based on your detailed description more than likely you have "soft seized" the engine meaning due to the lack of lubrication the friction generated enough heat for the metal to expand and tempereraly locking the parts in place.