Do you need a planner for resource consent?

So the Jan floods showed some weaknesses in our property and we are going to install a new drainage solution (incl retaining wall) to avoid any future issues. Unfortunately it looks like resource consent is required and the builder who will be helping us has intro'd us to "his planner" who is quoting $5.5k to assist. Do we actually need one or this something we can just handle with the council ourselves?