Vehicles are immensely complex and consist of thousands of parts. Auto engine repairs can be intimidating, especially if you're not a trained mechanic or don't have a lot of experience with engines and the like. That said, with patience and practice, many people can work on cars and even rebuild engines.
An engine rebuild is one of the most complex jobs a mechanic can undertake. Essentially, it means taking the engine out of the car and then taking it apart piece by piece. Once you have all of the pieces separated, you can replace worn out parts and rebuild the engine. Often, after an engine is rebuilt you'll get many thousands of miles more out of it.
You're going to need the right tools to rebuild an engine. That includes not just a wrench, but also equipment to remove the heaviest pieces. Also, organization plays a big role in motor repair. You need to carefully track each part. Otherwise, things could get lost.
Sound intimidating? The first engine rebuild does indeed take a lot of time and effort. The good news is that you'll learn a lot along the way.