Heli-Coils? anyone used these?

[yaris2010RS]

so im kinda new to these things, and when i say kinda new i mean never heard of them till someone recommended them :D

ive done a bit of research but bottom line comes down to i have no idea what to do with these things. ive watched a few videos online (youtube) but im still not 100% sure it will work that easy

story: i need to heli-coil one of the bolts on exhaust header. for those of u who have used heli-coils before where would i start to installing them and is there even enough space behind the engine to work without the need to remove the engine?

it was also recommended i heli-coil all the bolts is this true?

and when i heli-coil do i use the same size bolt or would i have to change size accordingly?

any advice would be great and more then what i know.

also would toyota do a heli-coil install for this, are heli-coils a professional approach to an issue like this or is it a back yard mechanic bandaid fix? im really considering putting the stock header back on, taking it to toyota and saying "i dont know what happened, i hit a bump it made some noise now fix it under warranty please" lol