I would suggest that you do a mock due diligence exam to see where your company has strengths and weaknesses. I would then put together a plan for what to do that will give you the biggest return for the least amount of money.
You will want to do a financial plan to find out if you can afford to leave your business. I often find that even though owners want to set a succession plan in place they haven't saved enough money outside the business to execute on the succession plan. Financial independence planning is an important part of the exit planning process.
You need to know who you want to transfer your business to. If you're transferring your business to managers or children you'll likely use a very different strategy than if you want to sell your business to a third party.
Depending on where you are in the process and the size of your transaction you'll want to put together a list of outside advisors you want to use. Having a conversation with an experienced succession planning professional can help in evaluating your needs.
You don't need a formal plan. You do need a planning process that will provide you with a positive outcome. The act of leaving your company has many moving parts. The more you understand what those parts are the better you're outcome is likely to be.