Questions on planning a pasture

I hope my questions aren't terribly stupid, but I *am* new to all of this; I figured the collective knowledge in this forum would provide good answers for me :) If you think it should go in the Poultry and Livestock forum, just let me know.

Our future plan is to buy a cow/calf pair for milk and slaughter (the calf). Since I'd like to do it primarily grass-fed, and I've been reading about Polyface Farms pasturing processes (rotating pasture, building the grasses, etc.), I'm thinking that I should start planning and planting the pasture this year in preparation for Spring 2010 introduction of animals.
Is this incorrect? When you plant for pasture, do you also till the ground like you do for a garden, or do you just toss the seed out there in broadcast manner?

For a cow calf pair on a two-week rotation, will five acres be enough pasture to lease? How much pasture should I allow them access to (how to divide up the pasture for rotational grazing) during each two week period?

What recommendations would you offer in regards to seeding the pasture - what varieties would you plant? Currently I think it is all blue fescue pasture- I would like to add some clovers and other varieties of grasses, but I'm not sure what would be the wisest choices. I also want to try to grow some mangels and some sorghum for them. We would only keep the calf until late fall, then slaughter and only support the mom for milk over the winter. If I understand correctly, I could breed her again when the current calf is about three months old, and that I should let her dry up about 2-3 months before she is due to calve again to give her body a rest.

I'd prefer a heritage breed, because I don't need the kind of milk production that a Holstein or Jersey gives - and I intend to let the calf stay on the mother until weaned rather than taking it off and bottle or bucket feeding.

And if you see any errors, feel free to point them out (gently...please...LOL!)

Thanks,
~Sunny