I managed to learn it all on my own; I rebuilt an engine too, but it wasn't some junkyard car's, it was my wife's car that she had gotten caught in a flash-flood and seized the engine on (see: "hydrolock"). Worked great for another 90k miles after that and was still running great when she sold it.
All you need is the ability to read, the desire to learn, the courage to get your hands dirty and not be afraid of breaking things, and some mechanical aptitude. And a little money to spend at Harbor Freight for some tools.
One of the rods was bent, and the valves in that cylinder were also bent because the piston had struck them. I still have that bent rod/piston in a box somewhere as a souvenir: the bend was pretty significant.
What's weird is my wife actually managed to get the car restarted after a while, and drove home that way!! It was making a terrible tapping noise though. I'm not sure how it was running that way; I didn't investigate too closely. This was a 2000 Acura Integra GS-R, by the way.
Anyway, I left everything alone in the other 3 cylinders because that all looked fine, and I replaced the piston, rod, and journal bearings on the bent one. I also replaced all 4 valves. It wasn't really that hard; I took the head and new valves and valve seals to a shop that specialized in rebuilding cylinder heads and they cleaned it up (it already had close to 100k miles at that point, so there was a lot of carbon build-up) and replaced the valves. They also put together the piston and con-rod for me as I didn't have a press for that. Then I just did the standard bore honing and put it all back together (and cleaned up the domes of the other pistons while I was at it). Worked great after that. The total cost wasn't much either; the bare parts only came out to a few hundred IIRC, from one of those online OEM parts sellers, and the shop work was $250 IIRC. The only specialized tools I needed were torque wrenches (which you should have anyway, but they're absolutely critical for engine work), and an air impact wrench (the crankshaft pulley bolt on that car was a real bear), and a drill-operated bore hone (cheap).
When the car's brand-new, you probably can use a foot-long breaker bar. Over time, though, they can get seized.
I have a breaker bar, but I haven't used it ever since I got an impact wrench. You can put a lot more torque on a bolt with a handheld impact wrench than you can with a giant breaker bar; they're really a quite remarkable invention when you think about it. The one I have (1/2in drive Ingersoll-Rand titanium body) has 1000 ft-lb IIRC.
All you need is the ability to read, the desire to learn, the courage to get your hands dirty and not be afraid of breaking things, and some mechanical aptitude. And a little money to spend at Harbor Freight for some tools.