Just file online Type N-400, then print it, make an appointment online for immigration assistance, bring it to the immigration office and have it corrected. They will teach you, correct what you have printed. Just tell the immigration officer that you can not afford to pay a lawyer. It is free. Go home,re-type for final correction. Submit bring your money, they will check again if you fill it correctly, if everything is correct, they will ask you to issue Checks. If it is wrong they will correct it and asked to re-submit again and bring the money next time. Once they accepted your check, in 3-5 days you will receive in the mail the receipt together with the REVIEWER DISC. Listen everyday while driving your car. When ready asked for actual examination.