Goran.. Congrats on the new plane.. sorry about your problems with it though! it happens to all of us some point (A LOT of points) in this amazing hobby! But believe me when things are going smooth you'll love it!

Umm about the plane,

Engine: where did you buy it from? a big name store will replace your engine for free if you tell them what is happening with the prop shaft threads, if not then contact the engine maker.. the running problem happens from time to time when breaking in a new engine.. you'll get it dialed in!

servos: Don't worry about the servos.. if all seem well then they'll be fine... if you want to get new high end servo's for safety then go ahead but hangar 9 won't include servo's that will just STOP WORKING.

If you choose to send in the motor for repair or replacement I suggest going to buy a RTF Parkzone Slo-V, Supercub, or a GWS Slow Stick and get some stick time in! all great planes to start and very gentle flying...