I replaced both coolant and A/C lines in my rear Heater and AC. Used rubber for all lines with steel fittings for AC. If you can DIY yourself, you can save a lot of money, because this is a labor intensive and big job. I bought tools and parts off of internet.

But first things first: inspect that your evap and heater are not rusted. I replaced these. Hose bibs were rusted, electrical connections too.

After everything was tested and leak-free, I created an insulated weatherproof trough (sheet-metal) for these lines front-to-back. It ended up better than OEM which are open to the elements underneath.