It will take sometime to sink in but this will be a boost to both Nani and Rooney. With Ronaldo gone I don't think Sir Alex could play trash like Park and get away with his offensive impotence. He'll start playing two out and out speedy wingers bombing down the wings, assisted on the flanks by Rafael and Evra. Rooney will play in a central role where he is scoring for fun right now and Berbatov will see more of the ball in play making areas. Tevez might be brought back too.
I disagree with the assessment that Nani is a failure. He's just not been given the burn he needs to get a consistent streak going. I remember him holding the fort with some wonder goals when Cristiano was injured at the start of the season but after that the game just became too tactical for Fergie to risk putting him in. I'm pretty sure if given a constant burn and entrusted with enough responsibility, Nani will score around 10 - 15 goals this season. Rooney's tally might finally break the 20s and Berba will add to his tally too.
Re: YouthNow Sir Alex has never sold a player without a back up plan. It was only the sudden departure of Roy Keane that he had not foreseen. When we lost Beckham he just brought in a 17 year old nobody knew about and turned him into the best in the world. Now he has that talent to work with again in the likes of Rooney, Nani, Anderson, Rafel, Fabio, Ljajic and Macheda. I'm pretty sure these guys will make great footballers and while they might not have the same impact as the Kids of 95, I predict to see atleast 4 stars from this bunch excluding Rooney who's already up there at the moment.
Re: The transfer budget.It is rumored that Sir Alex has close to around 110 mil GBP to strength the squad now. 80 from the Ronaldo deal, which is a pay upfront no strings attached deal mind you, another 10 mil gathered from selling academy players and finally the 25 mil he was given by the board to strengthen the squad with Ronaldo in mind.
The players that I have in mind:
1. A cheeky bid for Torres. Liverpool won't sell us but still I wouldn't mind a 50 mil GBP bid for him just to check their intentions and if Barca did business with Madrid then why not?

2. Sell Berbatov if planning to buy in a another world class striker that fits our counter attacking game. Someone like Villa, Benzema, Eto' come to mind.
3. Make bids in the 40 mil GBP range for one of Xavi/Iniesta. I wouldn't mind going close to 45 for Iniesta. They are unsellable for Barcelona but hey look at the money we have to spend.

4. Stay the F away from Ribery. Not worth it and any money will be overpaying for a 27 year old who hasn't managed a deep champions league run with a team.