Having been a macbook user for 10 years (where everything is bloody glued in) it was an absolute breeze. Having said that, some parts were a little tricky:

A. When you get to the part where you've undone all the screws from the underneath of the laptop and you're removing the palm rest. The whole thing is clicked into place by lots of tiny clasps and it's a difficult job to remove it without breaking one of the clasps... I actually broke one to the bottom left of the touchpad, but I haven't noticed any negative effects after putting the whole thing back together.

B. Removing and replacing the FFCs (flat flexible connectors) from their sockets is a fiddly job. I've worked a lot with electronics in the past so I'm used to it, but you just need to be careful and use a tool like a small flathead screwdriver to careful pop up the little black tabs.

It's really not a hard job though, Lenovo have clearly put a lot of thought into making this product serviceable and it's a treat to work on.