Most stuff in engine rebuilding boils down to competent machining, paying attention (take notes, stamp parts etc.) from the moment you start disassembly, until it is back together, and most of all thorough and methodical cleaning, then keeping things clean. Everything in the bottom end has one way it can go, or is marked one way or another (usually numerically). If you plan 4x the time you think you will need for your first assembly and try to enjoy the process it will go great.
The top end is even less complex, it is usually just a matter of a lot of time and patience.
There is nothing hard about building an engine, just take your time, pay attention to the details, get expert advise if you don't know, or a use a manual.