Hi,
1. About 2-3 years,
2. When I cancelled
Sky.
3. A bit of both, Installations as logical progression of my hobby.
4. Quite a short time, if you have been messing about with your own setups for a while.
5. There are courses run by the CAI for example. But the practical approach is good, actually try and set the systems up you want to install yourself, and get them working, see what can be achieved.