If you plant sweet corn, make sure it is at least 2 weeks different maturity from your field corn. If they cross pollinate, the sweet corn will likely not taste as good as it could. Raccoons, woodchucks, and other pests also seem to find sweet corn in plots, so you may want a little extra protection around it if possible.
It takes about 35,000 seeds for 1 acre of field corn with 30 inch row spacing. Seed size varies by bag and hybrid, so it is best to let the ag supply store know your plans so they can advise you on seed selection.