I still repair my own, and I just dropped the better part of $3000 dollars on a Snap On Solus bi-directional scan tool...
my garage is better equipped than most shops.
But I agree with the above, the industry has changed so much that diagnosing by a noise or a condition is a guessing game. The information they were giving in re-runs was vaild 20 years or more ago, but not in today's world.
Try to replace the rear brakes on some newer cars, unless you have the ability to go into the computer to command the caliper to retract the pistons you'll never get the new pads over the rotor
My neighbor was having trouble getting his 2013 Vette w/ 9K miles on it to start.... I tried to help him using my time honored troubleshooting skills.... this was right after getting off a 4 hour flight so my mind was scrambled.... after 20 minutes of testing battery capacity, cable condition, putting a new battery in the key so the computer would see the right RFID code to allow the computers to fire up (that was half the problem) it dawned on me that it was a newer car and I needed to use a newer car truth chart to trouble shoot it.... and after I swapped the rear defroster relay with the starter relay I got it to run, but it still took me the better part of 45 minutes to fix it... when it should have taken me 20. If I had my scanner with me I could have plugged into the OBD2 port, let the scanner ID the car and load the software, and I could have pressed one screen prompt to tell the computer to energize the relay and if it didn't start I would have gone straight to the relay