A CPA is an individual who is certified by the state to act as a public accountant based on a test and experience as a noncertified accountant. Many CPAs specialize in taxation, but many do not. Representing you is the specialty of a lawyer. Return preparation usually is not. Your lawyer may prepare your return as a courtesy, but most don't seek this type of work.
Various organizations offer tax assistance for elderly or low-income taxpayers.
In terms of qualifications, these folks are probably most like storefront preparers, but this could vary a whole lot. The big plus of a clinic, of course, is that the fee is usually zero or quite low. Your best bet is to ask your friends. Find someone who is happy with a preparer's work and get the preparer's name. Friends in similar financial situations are the best source.