Hi Inga,
It's work, it would feel challenging to a first timer - but it's not something you should shy away from if you feel up to the task. The monetary savings can only be compared to what your local repair shop would charge you.
Here are some things to consider, an electronics tool kit such as the one sold by ifixit is very helpful, and at a minimum, a screwdriver kit and some kind of prying tool is needed. This guide below is for the P8 Lite, but it will give you a good idea of the work involved to take it apart:
[guide|45850]
ifixit also sells the screen replacement you need at $55+shipping:
[product|IF338-018]
If you have absolutely no tools, it might be cheaper or close to same cost to pay for repair service locally. However, the toolkit is forever, and so is the experience.
I hope this helps to give you a general idea of what it entails