First, you need to talk to a REALTOR, who can do a CMA (comparative market analysis) for FREE. An appraiser will charge you $400-500 and will NOT tell you what you need to do to sell it. An appraisal just to have an appraisal is a waste of money. Plus, any buyer is likely going to be getting a mortgage and their lender will require their own appraisal (that the Lender has to order for the Buyer). They can't use yours if you order one.
Talk to a couple good Realtors and get their opinions.