I don't think Man United will "struggle" mate, not with Ronaldo, Rooney (no side with that chav football marvel will struggle), Ferdinand, Heinze, Van Nilsterooy etc in their ranks but they need some more quality and to get rid of some of the chaff. I would sell:
Fletcher
O'Shea
Saha
Smith
Silvestre
and bring it some decent players. Ballack maybe or, to be honest, Carrick from Spurs, another attacking central midfielder or right winger, another striker (why didn't they buy Owen?) and another quality centre half and left back (possibly Bridge).