Use the FileManager.Open() and FileManager.Save() methods to open and save your files.
To open a file:
fm = MaxPlus.FileManager fm.Open(MaxPlus.PathManager.GetTempDir() + r"\test3.max")
To save a file:
fm = MaxPlus.FileManager fm.Save(MaxPlus.PathManager.GetTempDir() + r"\test.max")
To get the file name and its path, use the FileManager.GetFileNameAndPath() method:
print fm.GetFileNameAndPath()