-How old is this system?
-What type of soil do you have?
-Have they opened the tank and verified that waste is properly moving to the tank from the house?
-Has the tank been pumped regularly and/or recently?
-Have they done any exploratory work in the field lines to assess them?
Things are tight economically, and while removing and replacing the whole drain field should ensure it works properly again, finding out WHY there is a problem an WHERE it is may show that complete replacement isn't all that necessary. But they would LOVE to just do the whole system.
+1 on getting multiple quotes but don't just say that you NEED the field replaced or that's what they will want to do. Ask them what is wrong and what it takes to fix it. If you take your car to the shop and tell them you want something
replaced they will do that; but if you take it in and ask them to
fix it, they may take a different approach to the job and save you bucks. They LOVE it when you make calls that you don't understand. I know of a guy that took a Chevy Silverado in for work and said 'replace the transfer case it's stuck in 4 lock'. So they did, for more than $1500, but the actual problem was the electric actuator on the front axle, which was $100, which they ate for the labor bill on the replacement, but they kept the transfer case. I know this because it's now in MY truck. I got it free from them.