A Lawyer Isn't Required
When you understand the rules about how to change your will, you do not have to have a lawyer. You just need to be careful that you are making the changes correctly and that the formalities to make the changes valid have been met. Even if you follow the rules, it is possible that someone will challenge your will and allege that you were not the one who made the change. Remember, when you are gone, you are not available to tell the probate court what you wanted.
While not necessary, sometimes enlisting the help of a lawyer is in your best interest. If you have your lawyer change your will, she will talk to you about your changes and have you sign your will or codicil in the presence of two witnesses and a notary. The lawyer and her staff will be available to testify, if needed. This assures that the changes you want will be found valid after you are gone.