I had never heard of a spanner so I looked it up. I guess that means a wrenches.
Anyways, really the best way to learn is to get a entry level or apprentice position with a local bodyshop and work your way into it. Observe how the pros do it. Of course back when I started there wasn't the internet so now you can look at videos and forums to also help you out.
Although you can just dive in at your shop but it's hard or unless you spend a lot of time online. Even at that it would be tough
Bodywork, prep and painting are fairly easy when things go as planned, it's when the don't that a noob would have a problem. So it's good to have the 'pro' nearby to help out.
I started in a tech school, then went co-op which meant I went to school half day and real world work the other half. I did the co-op thing near the end of the school courses