Do NOT use Lending Tree. They are a lead aggregator and you will get calls from every mortgage hustler in the country. Ask your agent for a referral to a good mortgage broker. Compare his/her costs with your bank and credit union, if you have one. Look at pricing on Aimloan.com. They are a cheap, internet-only lender, and should be among the least expensive, if you are a cookie cutter borrower (W-2 income, not a lot of fancy tax write-offs).
Once you have done that, you will have a good understanding of how to shop for a mortgage. If the broker is good at the job, s/he should get you the best pricing.