Stephen Colletti is gearing up to welcome his first baby with wife Alex Weaver — and he’s been turning to friend, collaborator and new dad James Lafferty for advice. “I have been leaning on him,” Colletti, 40, told Us Weekly exclusively ahead of the season 2 premiere of his and Lafferty’s show Everyone Is Doing Great. “I’ve been watching him forge the path of fatherhood, and I’ve been so impressed with what he and [his wife] Alex together have b…