very very difficult. it's more expensive, but your best option is to buy an assembly from fonejoy.com, and replace the whole lcd assembly.
I did that, then sold the old one with the cracked display on ebay for around $60 to help offset the cost of the new screen.
I went with fonejoy because it is genuine MS parts. I did not want aftermarket for this device.\
the complete LCD swap isn't too hard, but the glass only is almost impossible for the average DIYer.
Guys - is there absolutely no way to just replace the glass on my cracked 950? Everything is perfect except the cracks through the screen. I've only had it 1 week and don't want to spend almost the amount I've spent on it repairing the screen!! I bought replacement glass already.
Ideas???? Please don't make me use my iPhone!