Got to agree with FLoRolf here if you've got zero experience with 3d modeling then I'd start with something far simpler. Maybe start of with just trying to create one of the towers and see how you get on with that first. This'll also give you an idea about how long creating the entire scene will take.
Take a look at this vid to see how much detail this guy achieved in around a 100 hours of work in blender
Personally If I was making this and had to model all the assets from scratch and texture them, I'd probably want at least a week to do even a half decent job at recreating this and I've got over 15 years experience with 3d modelling.