Need to replace insulation / plastic covering underneath of travel trailer

[bwt74]

I have a 2006 Cherokee 28A Travel Trailer and I have recently had a water heater burst and leak all over the subfloor and onto the plastic and insulation barrier underneath the camper. I had to remove sections of this barrier to allow the wood to dry out.

I am replacing the water heater, but what's the best way to replace the Plastic/insulation barrier on the under carriage?