Welcome to the world of windshield repair. A couple of comments regarding your post:
(A) The training videos supply enough educational content to show you technique. However, if going to a training class is not possible, then I suggest going to a junkyard and practice until you get good.
(B) The fellow that you mentioned going out of business probably did not close due to having to replace a windshield. Its more likely that he thought this was an easy money job, and found out the harsh reality that it is work, and like anything or any proffession you must be good at what you do or you won't survive.
I am really appalled at some of the Manufacturers advertisements that suggest you can become an overnight success and be in a 6 digit income bracket in less than a year.. I'm not saying it isn't possible but I will say, it will require a huge effort, salemanship, people skills, and 60-70 hours a week. The down side to this business is inclement weather, insurance (garage keepers, glazier), and competition willing to do shoddy work at half of your price. To the unknowing customer, shoddy work is great.... Until it spreads. The waiver issue has long been a forum debate.. Safelite has every customer sign a waiver prior to work being started.. Myself, I do not believe in waivers.. I am confident enough in my skills and abilities to do a proffessional repair or be honest enough to explain to the customer that their damage may be beyond repair to not need or want to use a waiver as an excuse. I (in my opinion) think to many shops use waivers as an excuse for doing shoddy work (as stated earlier, the customer doesn't know better). And I am against it..
In closing, alot of useful information can be found at these forums. Some of the same questions you may have, are already answered from a previous newbie's question. The thing to remember is: There is no such thing as a stupid question, Although some of the answers... LOL.. Good luck with your decision.. And work it hard, your success depends on you..