Generate a full detail guide that provides a high-level overview of the M&A process for small businesses. The guide must be structured and clear. It should include sections on: 1. The Seller's Perspective: How to prepare your business for sale and the valuation process. 2. The Buyer's Perspective: A guide to due diligence. 3. An overview of the key stages of a deal (from Letter of Intent to Closing). 4. The critical role of advisors (lawyers, accountants, brokers). Please include a very strong disclaimer that this is a highly complex process requiring professional expertise.