Heli coils are pretty simple, you must have enough material to drill the hole oversized to tap it for the coil and you need to measure the depth of the hole. The best would be to be able to be deep enough to use the entire coil but Have cut the coil down in the past to shorten it for a hole that is not deep enough. also the hole MUST be drilled strait and taped strait. If any of this seems too much for you have a professional do it.