Intervals and other types of speed work are essential to improve running speed.
You train best where you are the happiest.
You have to forget your last marathon before you try another. Your mind can't know what's coming.
Running with others can help get you out when you might otherwise blow it off.
For the novice runner, I'd say to give yourself at least 2 months of consistently running several times a week at a conversational pace before deciding whether you want to stick with it. Consistency is the most important aspect of training at this point.
I think he had a wake-up call. It's a different kind of race, and I think maybe he didn't take it quite as seriously as he might have, but you can bet he learned a lot of lessons.