I think the European experience is important in the sense you have a lot of games to play, and of different importances at different stages of the season. How you rotate the squad and how strong team you take to other teams, how you set up against French sides, or things you need to remember about German teams, are all little tricks that are going to come with experience that ensure you can run both campaigns side by side without detriment.
I think Moyes will be okay, he's got plenty of experience in how to manage a squad throughout the season, his Everton teams the performances he got are proof of that, he's got a bigger and better pool to choose from now. As for the experience, United do have the benefit of having Sir Alex about the club if Moyes did want advice, plus he has people like Giggs and Neville in those roles who have recent experience he can talk to. Most of the squad don't need hand holding, Vidic Ferdiand Evra Carrick Rooney RVP, even Nani and Anderson are seasoned pros in Europe who have faced plenty of these players before. Moyes will have some to learn but I don't think its a Harry Redknapp at Spurs job, plus we don't realistically have a chance of winning the CL so we've probably got 2-3 seasons at least where the quarters are as far as we are going anyway.