Face it, the mechancs of a bicycle aren't that complicated. If you can get the shifting adjusted so that it shifts, and the brakes so that they brake, and get all the bolts tightened so nothing falls off, there is nothing a "professional" bike mechanic has over you. There is no hidden mojo or some unspoken trade secrets in there that cause a layman to never achieve the level of someone who does it for a living. Especially not when there is no baseline; not even in countries where the concept of vocational training is historically more organized and standardised than it is, to my understanding, in USA.
I, being the owner and vthe user of a ike i care about, will possibly be more dilligent and picky about the quality of my work...