No attorney is strictly required for your case. If you have evidence and prepare well, everything should go smooth. A good attorney in your case can only help keeping conversation and questions to the point. E.g. if IO asks irrelevant question, your attorney could help by pointing this out to the IO so then they'd stick only to what is necessary to adjudicate the case. If you have money to spend on attorney, there's nothing wrong with hiring one. But not required and optional in your case.