回複：再問老師, L/C, PERM and I140是律師辦的. I-485能否自己辦.

Yes, you may file I-485 on your own.

When you remove the G-28 from package, be sure you need to cross out Part 5 and right bottom corner of 1st page of the form. They're attorney related information, and would result in a return if no presence of signed G-28.