sorry, never heard of self tapping bolts, as for taking the head off i cant help with that either, never had one of those but it might be an engine out of the frame job if you dont have room to lift it clear, the main thing is to slacken the cam chain adjuster and lift the head off without dropping the chain...DONT drop it into the crankcase, tie it up somewhere, after you do the repair you need to put it on in the right place.
If you do helicoil it you will need one of These
You need a dead steady hand when drilling the pilot hole and make sure you keep to the correct angle and depth, if youre not sure or confident ask your local engineering firms, they might do it for you but you may still have to buy the kit. Dont use bolts in the exhaust, use studs with nuts, that way the thread in the head will not be damaged