If you were applying for a green card in the past, you could do it yourself. However, today you need competent counsel to help you.
Our current government is changeable, as evidenced by the new eighteen-page I-485 Adjustment of Status form–as opposed to the old six-page form. Now, the need for an attorney begins before you submit that application, not after when you encounter problems.
When you decide to marry a US citizen or non-citizen, that’s when you need to talk to an immigration lawyer.