My wife is a long time Florida Real Estate broker (and Hawaii licensed sales associate). I'm a licensed FL sales associate.
Unless you are very experienced with Real Estate deals don't do it without some sort of professional representation. Most states have required disclosure laws, some even federal disclosure laws depending on the age of the property. Know what your state requires and disclose to the buyer.
Real Estate laws vary by State. Advice from someone from another State isn't worth much.
If you use a lawyer definitely use one that specializes in Real Estate law.
Many real estate lawyers own their own title companies, so you can use the same attorney to write your sales contract and do the title. (Two separate fees there, but well worth it, if you're not using a Realtor you've negotiated a fee with to do the contract. In Florida, title companies do not write contracts, real estate attorneys or Realtors do. Well, technically Florida and Hawaii Realtors don't "write" contracts. They "prepare" contracts approved by their respective Realtor Associations and their state attorney BAR associations. In FL it would almost always be what's called a FAR/BAR (FL Association of Realtors/Florida BAR) contract, which is what most lawyers will also use. The same is true in Hawaii and many other states.
Real Estate brokerage fees are negotiable. If you already have the buyer you should be able to negotiate a VERY favorable rate. Going through a brokerage can offer a lot of peace of mind and great reduction in aggravation as well as liability and other protections.
The on-line Real Estate sites such as Zillow and Trulia are notoriously inaccurate and generally outdated. Yes, look at those sites. NO, don't base your decisions on them. Often a Real Estate brokerage will do a CMA for free. A CMA is not an official or legal appraisal but when done by a competent agent, it will give you a very good idea of property value. CMA = Competitive Market Analysis. Don't trust an on-line source for that.
Good luck.