As a result your AM.xml and AMClient.java will be modified (it will actually add the entry for the exposed method). This is fine and works good.
However, if a need arises to modify this method's signature then you should not directly go to your AM.java and modify it straight forward. Doing this may corrupt your AMClient.java file and leading to issues.
The right way is:
1. Open you AM and go to java tab.
2. Shuttle the method whose signature is to be modified towards left.
3. Now modify your method signature. save all.
4. Open you AM again and shuttle back the method.
You will also need to delete the method from the pageDefinition file where it is used and refresh the data control to add it again.