biggest question I have right now is: What do I need to know about getting the most out of land that has a mostly northern aspect (generally north-facing)? My long-term goal is to develop a diversified and somewhat nut-and-fruit tree based permaculture operation over my lifetime. Background about the land includes that it is sandy loam, zone 4, rolling hills (one high point 150ft. and other rises measuring around 75ft.), with a mostly north-south rectangular orientation. It is now and will be operated as a grass-fed beef and hay operation for the next few years.
Mark: Think about this for a minute... There are plants growing on every slope with every aspect to the sun on every continent in every climate on this planet... From what I gathered, it seems to me that you're somewhere in Wisconsin USA, so you've got lots of choices... If it's currently in hay and is grazed, do a Silvopasture system:
http://nac.unl.edu/silvopasture.htm
IN WI you can do the "classic" oak savanna Restoration Agriculture model as described in the book (Chestnuts, apples, hazelnuts, raspberries, grapes, currants and livestock). The aspect to the sun will have a factor, in fact it might be a better place to put cherries, apricots, plums or kiwis because they will probably emerge later in the spring and not be as likely to bloom early and get nailed by frost.