Everyone has to start with their first engine. It really isn't that hard. You just need to have some patience, take your time, and double or triple check all of your work each step of the way. I recommend purchasing a good book on rebuilding modular engines before you decide if this is a project that you want to take on. That will give you a better understanding of the process and will help you to determine if you have the necessary tools, skill set, desire, etc, to do the job correctly.
I built an engine for my truck 20 years ago. 400k+ miles later, and it still runs pretty strong!
There is a great deal of satisfaction when you turn the key, and and hear the engine that you assembled yourself, fire up and run... But there can also be a fair amount of frustration if the rebuild is done incorrectly.