Well, I still feed Ruby at home, and she gets whole milk at school....and formula while we're out (because I am tired of carrying a cooler pack in the diaper bag!) but how whole milk was introduced was that a few weeks before her birthday, she was out of backup formula at school and I really had no desire to go and take them some, it would have taken up the rest of my workday and I couldn't afford to do that, so much to do! so they asked if they could try the milk and it was a hit. it was straight milk, no cutting it with formula or Breast Milk....and that's all she wrote. I do buy it at home and she'll get it a few times a day, but one thing to remember is that if they get too much, it's not so great. I think 16-20oz is max, but since they're eating solids so much more, that should be about the amount they'd take anyway!
As for sippy cups...ahhh, haven't mastered that one yet. We've been trying to get her to take white liquids in them for a few months, knowing today would come. You see, today, she moved up into the new class at school where they use ONLY sippy cups. They've been working on it in the infant room, but she's still addicted to the bottle. I won't be at all sad if she takes to the sippy cup immediately while at school and refuses bottles....I cannot WAIT to reclaim my counterspace! LOL but yeah, if he's the type that will take what he gets, then go cold turkey, but if he's like Ruby, it'll be a transition. I would personally recommend, since you're doing both at once (whole milk and sippy cup) is to give him the whole milk IN the sippy cup and never in anything else. and do the replacement thing once a day for a few days, then upping it and dropping a bottle every few days until he's off the bottles.
It's never as easy as other moms tell you and it's never the same experience twice. So good luck and keep us posted :)

(Thanks Lorry (lorryfach) for my siggy :D)