I have used helicoil insert kits on several bikes and they work a treat, like you say if you can get access to the area then mask everything off and also have a vacume cleaner ready to suck up the swarf and bits
There are other brands of insert which i think i remember Bryanj mentioning which are supposed to be even better than the helicoil
I bought a cheap kit on ebay which had everthing i needed to do the job
Pete