In some states, you do need an attorney to complete a real estate transaction, but in others you do not.
Most home buyers are capable of handling routine real estate purchase contracts as long as they make certain they read the fine print and understand all the terms of the contract. In particular, you should be clear on the terms of any contingency clauses that will allow them to back out of the contract.
If you have any questions at all, it may be advisable to consult an attorney to avoid future legal hassles. In looking for an attorney, ask friends for recommendations or ask your real estate agent to recommend several. Call to inquire about fees and to check on their experience. In general, more experienced attorneys will cost more, but real estate fees as a rule are small relative to the cost of the property you are buying.