Your friend is right IMO. Do something simple first. Like a broken piece of trim, replace a light bulb, change the wiper blades yourself and build yourself up. I had repaired bicycles/motorcycles before hand.
Past that. I literally go on YouTube and watch someone do the task I intend on doing. I have the service manual downloaded for the car (people dump scans of the manuals online as PDFs) and a Haynes Manual (about £20).
Over the last 6 months. I've gone from barely being able to change the wiper blades to replacing a turbo.
I bought an older vehicle(s) that have a good aftermarket parts market and are known to be easy to work on. The simpler / less refined the car is the easier it is to work on.