Cost to replace septic system in Minnesota?

My mother has a very old 2 bedroom house on one acre. The septic system is leaking through the ground. The house and septic sit on a very tall hill. She's had an enormous amount of rain saturating the ground. It appears her laundry water discharge went straight into the ground through a separate Perforated Pipe. But now that is leaking in a separate, but close location. Odd. Could she use a gravity septic system? Looks like they will have to dig under the house to access a pipe from the laundry and repipe the drain, but that is not an issue. She lives in Minnesota. I'm going out there today to look again. But I assume everything will have to be replaced. Will she need all that sewage earth removed as well?