It depends on the complexity of your situation. If your situation is fairly simple, then do it for free. I completely believe in saving a buck where a buck can be saved.
If you have something trickier though like self-employment, rentals, even itemized deductions, then you might want to consider a preparer. Just make sure that you ask around and find somebody your friends/family recommend because there are a lot preparers out there who are not qualified. My suggestion is to stay away from chains like H&R Block, Liberty Tax, Jackson Hewitt, etc. because many of them have brand new preparers fresh out of their tax schools who are confused about the tax laws.
A preparer can always help you with tax planning because once you build a relationship with them, they know your history and know what to look for and what questions to ask.
If you need a checklist to help you figure out what to get together to take in to a preparer, feel free to print one off of my web site on the tips and tools page.
I am a tax professional.
All answers given are based on our knowledge of tax laws and the information as you have provided it.