Welcome to the forum Scott,
What year is the trailer? Is it possibly still under warranty?
Mold of course is from moisture and it doesn't take a lot. You might have a plumbing leak under a sink you haven't noticed or it could be from repeated storage outside in cold and wet conditions, who knows.
For a fix you are going have to pull up the lino but because it is laid down before the cabinets are installed in RVs you have to cut around the base of all the cabinets to get it out. I would then make sure it is dried out well using heaters and then paint the entire floor with Kilz, that is if it sound and in good shape otherwise. Then I would lay down a laminate floor like Pergo or Bruce. Watch Home Depot or Lowes for close out flooring. They sometimes have great deals if they only have 1 or two boxes of something left over and it doesn't take much to do a small RV. We did our last motorhome for about $150.