I did this the other day on my TDI, it should have been easy.....
It was an absolute pig!
The insert would not go in no matter how much grease was applied and when eventually it did, it was done by pretty much jacking the car up on the insert so the weight of the car pushed it in!
And the results once it was fitted? Now I now this thing is meant to bed in but after 10 seconds of the engine being switched on it was clear it this wasn't the mod for me. At idle it felt like I was a brick inside a cement mixer the vibrations & banging was that bad, it was that bad we jacked the car up, spent God knows how long trying to remove the thing & refit it, only to find it made no difference what so ever. We then tried raising the idle speed to smooth things out at idle but even at 940rpm the whole car was buzzing.
Even driving with it fitted we felt every engine vibration possible, I'm sure over time it would break in better, but for me it was totally unbearable. The only option I'm left with is to possibly beat the thing to a pulp with a mallet to soften it more then fit it, or try to modify it somehow to bring it to an acceptable level of comfort. Plenty of people swear by these things, for me though it just didn't work.