I would not retake a B that you got freshman year. I would continue with your life and just not worry about it at all.
You are a very strong candidate for any university. Run the NPC for Cornell before you apply and only apply ED if the NPC shows that it is likely to be affordable. Make sure that you apply to at least one and preferably two safeties that are ABET accredited for your major (since you are intending to be an engineering major). Look for schools that are a good fit for you. I expect that you will do well.