Some EAs do accounting as well, and some do not. Attorneys had to study tax law in order to pass the bar exam, but only a small percentage provide tax preparation services on an ongoing basis. An attorney is also the only tax professional who enjoys client-attorney privilege under most laws, meaning that your conversations with them generally can not be forced to be revealed in a court of law. Some states license tax preparers, but may allow unlicensed preparers to practice as well. While there is no guarantee that a licensed preparer is any more knowledgeable than an unlicensed one, licensure does give you some reassurance that there is some outside government entity monitoring the person's performance.
Tax laws are complicated, and constantly changing.
If money is tight, consider that attorneys, CPAs, EAs and licensed preparers may charge higher rates than store-front tax offices and unlicensed preparers. And there is no real guarantee that they are that much more knowledgeable than the unlicensed preparer who does returns on her kitchen table. If you have a simple, straightforward return, such as a long form with itemized deductions, it's likely the storefront operations or unlicensed preparers can do a good job for you, at a fair price. Keep in mind that, regardless of whether you hire someone to prepare your tax return, YOU are the only one that the Internal Revenue Service considers responsible for its content.