Do I need a corporate finance adviser to sell my agency, or can I do it myself?

Advisers are expensive and I wonder if I can run the process myself

For a business of this size and complexity, a good adviser usually pays for themselves several times over, by finding and managing buyers, running a competitive process, protecting the price, and freeing you to keep running the business so the numbers don't slip. Doing it yourself is possible but risky: you lack the buyer network, the process experience and the negotiating distance, and the deal eats the attention the business needs.