In my case, since my Machinedrum is a bit older and out of warranty anyway, I took the risk and did it myself. Important note is, that I am not that much experienced with using a soldering iron, to give you a hint regarding the difficulty of the task. The only exhausting thing is the desoldering, since the screen is connected to the board with 20 pins. I can give you guidance and details if you want to, BUT:
Elektron can replace your screen with a white Monomachine screen, too
(and in this case, I ASSUME that this won't harm the warranty)
The price is around 150€-200€ (work and screen included) and you have to send the machine to Sweden. Turnaround for repairs are 2-4 weeks after they receive the unit.
If you choose to do it yourself, you can save a lot of money though. You can buy a fitting lcd screen in a electronic store for around 30€...
I can understand that you want to keep the warranty, though!