remember high school chemistry class? you can use a heated mix of alum and water to attack the steel stud without damaging the aluminum case. it'll pull the iron molecules into solution and just leave a brittle little turd of whatever alloying agents are in the steel. just don't let any steel you don't want gone touch the solution.
I just stick the part into a cake pan full of the stuff and leave it in the oven for a few beers. mine's gas so I don't even need to turn the thing on, but if yours is electric just turn it to whatever the lowest setting is.
if you've got the stuff to do it the easy way, go for it, but $6 worth of alum vs having to buy $30 worth of kit to helicoil it isn't bad