First, assess the thread damage. You may be able to just chase the threads with a greased tap and be back in business. I can't tell from your plug picture how much damage would have been done to the hole. But if the threads are too messed up, do yourself a favor read up on the "Time-sert" information.
Their insert is actually a smaller outside diameter than the helicoil ones, so there is less head material to be removed. There is also no drilling. You use their special double diameter tap to do all the cutting and rethreading in one fell swoop. The tip has a section that threads into the old damaged threads, then there is an enlargement boring section, and the final section cuts the new outside threads into the head for the insert.
Their longer reach spark plug re-thread systems are made exactly for this type of situation with deep spark plug wells. No special home-made guides are needed because it will align itself via the old buggered threads and hole. No tabs to break off because the solid insert is expanded in place to hold it using the tool.
This also makes a superior heat transfer interface, which is important for spark plug applications. The time-sert is actually harder than aluminum, so the threads will be better than new when completed. You just need to take your time and go at it easy.
As for the inevitable metal chips, make sure that the piston is down (per instructions, so you don't run the tap into the piston crown) with no valves open. Grease the tap well (goop it on) to make sure you catch most chips during cutting. You can also back out and clean the tap and re-grease it one or more times during the cut. When you're done with the thread cutting, attach a small diameter vinyl hose to a shop vacuum and feed the hose into the spark plug hole. Work it around in there to pick up any metal pieces that fell in. The rest will blow out the exhaust on first start.
PS - I have no relationship with Time sert. I just recently rescued a SAAB 9-3 that had blown the spark plug clear out of the aluminum head using this technique. I think that any competent mechanic should be able to pull off this repair. If the alternative is to remove the head and (likely) replace it with a used one, why not try the Timesert repair first?
PPS - After browsing your photobucket account, I think I can see the root cause of your problems.
You've got a car tire on that bike! :nono: Now, didn't we warn you about bad stuff happening with those things?
Sorry for poking fun in your moments of distress. But I just couldn't resist.
