Man, this is almost exactly how it went down for me. I lucked out and had a great mentor.
I was driving delivery truck and really wanted to build myself a computer. Not knowing the challenges back in the day, I built an AMD K6-2 machine with an Nvidia video card. Back then that was no bueno as Nvidia did not play well with non-Intel chipsets.
I went to the local PC repair guy for help. He was kind enough to help me and not charge me, to the dismay of his minion that mocked me for not knowing. We chatted for a while and had a friendly conversation. One day I thought, I would offer my services part time for free if he trained me. He took me on part time, paid me and showed me the basics. A couple weeks later he fired everyone working for him and offered me a full time position. I was still very green but learning. I accepted the job. I started taking in computers while he was on the road doing repairs. I took it upon myself to start the repairs or at least the diagnostics. I read some stuff online and after about a month, I was training him and designing builds.
He handed me the keys to shop and some networking books and told me that was next. I learned on the go, and started getting certifications after the fact. I don't do so well with book learning but hands on....all day any day. That is the way I prefer to train people at my current job. I can make a list and instructions but hands on always wins.