This is worth 100g for a reason. The song is not easy and unlocks near the end of story mode. It is 80+ moves of high energy jumps, turns and tricky transitions where few of the moves repeat. You are going to need to practice the song a lot to get this done the proper way.
There is a trick that you can use, though. You can unlock this in practice mode. In order to do that, you will need to devote at least a half hour if not more to this one song as a result of the high number and diversity of moves in the song. In this game, score does not determine how many stars you get, it is actually the amount of nice and flawless moves you get and the multiplier you keep. So, when you are practicing, try to pass as many moves as you can both in the breakdown and the recap. If you fail a move, you can always say "XBox previous" to replay the last move and try again to pass it. That won't work for the recaps, but hopefully you will have a decent enough idea on how to manage the moves by that point and can muddle through with a lot of goods. If you have met the 5 star requirement at the end of the song in either practice or perform, you will unlock this achievement. To give you some guidance, I had about 95% or the moves passed in breakdown and about 75% of the moves passed in the recaps with the majority of the moves being "nice." So you do have a fair margin in practice. If you are doing this in perform, you will need a score of somewhere between 1.9 and 2 million points (depending on what moves you miss).
I've included a video of a Youtube personality doing amazingly well in the performance mode, just to give you an idea of what you are getting into.