Most insurance agents will determine the replacement cost for you when providing a quote. I would bet that if you contacted another agent for a quote they would give you a replacement cost estimate. If you would like to do one yourself I am aware of a website by Marshall & Swift http://www.accucoverage.com/ where you can estimate the replacement cost for yourself for around $8. We are not affiliated with this company but we do use them with some of our companies to provide replacement cost policies for our insured's.
I know how you must feel. However, I will tell you this is more common than you think.
Unfortunately, these are the types of questions you need to be asking up front. Your Realtor and your mortgage person should have suggested you asked these types of questions when shopping as I do with my clients. You left your previous mortgage company over the interest rate because you were shopping for the "best deal" and what you saved on one end I hope does not cost you in another.
The best types of people to deal with in any industry are the ones that not only answer your questions, but have have enough experience to answer questions for you that you may have never thought to ask or that have the foresight to protect you from you.