If I would like to change my business from a sole proprietorship to an S-corp, can I do it alone or do I need a lawyer?

There is not a requirement that you have a lawyer to change your business to an S-Corp, but it's generally a good idea to do so because it can save a lot of future headaches.  Many attorneys offer inexpensive services for incorporation that will include a checklist of your annual filing requirements.  They can also help you make sure that your entity is protected from challeges by another organization.  Massachusettes has a requirement that the name you use not be confused with any other organization that is already in business.  They can also help you evaluate what type of corporation is best for your needs.  You mention wanting to convert to an S-Corp, but you may also want to consider and LLC depending on the nature of your business and your long term business goals.  If you decide to hire an attorney, find one that regularly handles incorporations-- they will be more saavy at the issues you need to know about and questions of business law.  Family law attorneys are nice people, but they may not be aware of the nuances that you affect your company.  Also an attorney that regulary does incorporations will be more experienced, require less time to do it, and thereby cost much less than an attorney who is trying to figure it out for the first time.