A change of pace in terms of your running pace will give you strength psychologically.
The marathon can humble you.
I believe you'll develop speed via strength work which includes hill running, either repeats, or running hilly courses as the Kenyans do on a steady basis
Every race is totally different.
If you want to win a race you have to go a little berserk.
I believe in keeping running simple and, in regard to shoes, that would mean no gimmicks, unnecessary cushioning, etc