The answer would be very simply, "yes." A company manual/employee handbook offers structure, accountability, protection and helps to map out expectations of the company. All businesses, large and small, need employees to be effective and to represent the interests of the company. A company handbook can be an excellent way of establishing the values, priorities, guiding principles, customer service expectations, as well as expectations for the employee-employer relationship.
The key to an effective company manual is to state the obvious. If an employee can be terminated for stealing or using profanity at work, be sure to state this in your manual. Although this may seem obvious to everyone involved (even the employee), an employer who doesn't write it down is open to losing unemployment cases and potentially damaging legal situations.
There are various websites that can provide you with assistance in writing a manual/handbook, such as www.bizmanuals.com or www.hrit.com.