Home heater and sewer pipes need replacement

Hello. We are the Lefebvre's. Our house was built during WWII, on an air force base. We've lived here for 12 years.  The sewer pipes under the house have been rusting severely, and cracking for the past few years, or so.  The plumber said we need to get them replaced very soon.  The HVAC heater system is about 15 years old, and is going out. We need to get these replaced asap. Winter is almost upon us. God bless you.