You can call any realty office(s) and ask for comps--a free service provided by most agents or you can hire a licensed appraiser. As for the loan--why not visit with any qualified loan officer(s), see what your budget can handle, look at your credit score and determine the best options for you.
If you have established a good credit history with your current lender, it would be the best avenue to go with applying for a new loan. Of course, you would still have to do another loan app. since it's a different property but knowing you've been a good borrower may hold some weight. They will also be able to tell you what you would qualify for with the new loan. This should be done before you even begin a search for a new home.
I would go under the "Find a Pro" tab on Trulia and research a local area Realtor. They will be able to provide you with comp's in your area and see what upgrades or amentities your property has versus what's been sold in your area. Listing your home at the right price will be critical in the sale of your home.
Check with your bank or a mortagage firm to check on what you would be able to do on another loan. Contact a local realtor for a current Comparative Market Analysis for a rough idea on the value of your home in today's market.