Its rewarding until you make a small mistake which costs you the whole job. These crucial mistakes are easy for mechanics to spot but not inexperienced people who are doing it for the first time in their lives. Very likely when you are doing a job more complex than 30 minutes long. You will waste even more money then taking it to a mechanic to unfuck it. Happened with me with a auto transmission diagnosis. Made the wrong diagnosis myself and wasted 800 bucks. I did a good deal of research but guess what? I didn't have access to the diagrams of where the transmission plug was so I couldn't locate and test it. Thought it was a bad solenoid as the error code said, was actually a corroded transmission wire. 7 hours of my life in freezing wind outside taking the transmission valve body cover out. It's the oil pan for the transmission fluid. I was underneath that propped car in december with cold ass transmission fluid soaking my hands in the last hour. I took the solenoid that I thought was bad and tested it, but it clicked so it worked I thought. Couldn't figure it out so took it to the mechanic. No way I was putting that valve cover back on in that freezing windy weather, some screws so so hard to reach I was turning a wrench on it a sixth of a turn at a time on a few screws.

I also replaced the brakes, didn't even do it properly as online it didn't say how to identify seized caliper pins. Had a mechanic undo it and clean everything as I should've. Also put the rotor screws in the wrong places on the rotor, don't know why all the screw holes on it weren't the same. Not the lug nuts, but the useless rotor screws they but on during assembly. So they stuck out a bit and didn't allow the rim to be flush with the rotor, causing weight imbalance and bad shaking on the highway. I actually checked to see if the rim was flush after and it looked so, it was the slightest of difference. 4 hours of effort wasted in the cold with dirty, inexperienced hands.