<p>Finaid has a loan calculator. <a href="http://www.finaid.org/calculators/loanpayments.phtml%5B/url%5D">http://www.finaid.org/calculators/loanpayments.phtml</a></p>
<p>No I don't think you are overthinking it at all. Depending on the amount of the loan it might make quite a difference in your total payments.</p>