and how does it work?

 

IIRC, it basically screws in and you can screw into it. Go to an autoparts store, they will know and explain it to you and give you the part.

 

The HC kit comes with a tap, a drill bit, an installer (which is a reverse thread do-hicky), and the tread inserts.

You drill out the hole to the larger size (which is the external diameter of the thread), thread it with the tap, and then reverse screw in the treads. Bingo, new threads.

A HC kit is about 30 bucks.

 

Actually, its a bit more complicated than that. You have to drill out the hole, tap it with the special tap the kit comes with, and then put the insert in. No fun, especially for what you are doing it on. FYI the helicoil kit is going to run you around 45 bucks.

Is the engine in the car?

 

It is not a fun thing to do, but it isn't too bad using the Heli-coil. In certain instances it is a life saver. I broke a bolt going to the thermostat housing. I couldn't get the rest of it out, so I tried to use an easy out. But I felt like I was going to break that off and then I would really be F****D. So I had the choice of either using the Heli-coil or taking it to a mechanic. So i used the heli-coil. Take your time, and follow the directions and it will work good.
Take care
Mike