Changing Screen and Touch unit without breaking the plastic chassis

Hello,

I have a problem to separate the screen and touch unit of the Lenovo Yoga 2 13" from the “chassis”.

I've received a screen with touch unit and want to replace it.

The screen is separated just like in the Manuel on this page (IFIXIT Lenovo Yoga 2 13").

But now I am afraid to broke the the Lenovo plastic-surrounding piece...

If somebody have a hint or some pictures it would be great!

Thanks in advance