My vote on the "outlaw" maintenance goes something like this: your mechanical experience is valuable, but you should not be doing repairs without the supervision or guidance of a trained A&P. You also shouldn't be afraid to fire your A&P if they're doing something that makes you feel uncomfortable: "I may not be an A&P, but I know enough to know that ain't right." Do it long enough, find someone to sign off for you, take the test and add the letters to your name.
I suspect that my engine failure a couple years ago was due to an assistant and not the guy who owned the shop.
Just about everything in aviation is high performance, lightweight, and designed to be operated at rated power/strength continuously. Your standard IO360 is an air cooled four stroke rated at 200HP. It makes that 200HP at only 2700 RPM, weighs 258 lbs, and is designed to run continuously at that output for the life of the engine: 2000 hours. I think of that like a high performance automotive engine being designed to run at peak output power for over 200,000 miles. Most normal category airplanes are designed to operate from -1.52 to +3.8Gs. Consider an airplane with a max gross of 3000lbs, as I understand it (and please, somebody correct me if I'm wrong), that the airframe, which may weigh about half that when empty, is designed to handle the equivalent just under 12,000 lbs of weight under positive G loading and flex to around -4500lbs under negative loading. I've encountered wind shear and turbulence that has put me close to those limits in flight. A combination of fasteners, adhesives, welds, et cetera, make up the airframe. Add in that there is specific knowledge surrounding the different components and purposes for each. A small nick in the blade of a propellor can lead to a crack and inflight separation. You are being carried at an altitude by a combination of thousands of parts, many of which are solely critical to keeping your ass in the air. Margins for error are less and the results of failures are far less forgiving.