I would get one.
My husband has been through about a half dozen modification cases, and only attempted going without an attorney once. After three modifications that we thought we could just do this ourselves. Big mistake. His ex's attorney pulled stunts that he wouldn't pull with another attorney. For example, inproper service, and trying to intimidate us into agreeing to terms the judge didn't award. If we hadn't used an attorney earlier, we might not have realized what he was doing, but we knew what SHOULD be done. Problem was - with no attorney we didn't have an easy way to hold the other attorney accountable.
We have used an attorney ever since then.