Re: Pergo floor first.
Although a coach is built differently than a school bus, I think a lot can still be learned from this site.
Some of us in colder climates have insulated our floors, but in a skoolie precious head room is lost when we add an inch or two to the floor. I'd imagine in your bus that's not such a problem. I would recommend insulating the floor. Last winter I stayed 2 nights in my bus when it was well below freezing, I had heat going but a strange thing happened. Near the ceiling it was probably 80* but near the floor it was below freezing, I could tell because when I woke up my blanket was frozen to the wall and there was ice formed on the walls near the floor.
If your camping in extreme temps I think insulation is well worth it, especially now before you've started your conversion.