We just got an 02 coleman pop up and we were wondering if we should do something like undercoat the floor because it's just particle board? and we have small unknown leaks around the front storage box that I'm not sure how to deal with. Does anyone have any great ideas?

Howdy and Welcome to iRV2.com

Its great to have you here, many of us Started in tents then moved to a pop up. Cheri and I have had 2 an old Viking in Alaska and a Coleman Bayside (Fleetwood). We loved both but needed more room to carry the goldwing.

I don't see anything wrong with treating the bottom, I am sure it is treated but adding more cant hurt. I would also use RTV or Caulk around any seams while your under the camper. As far as the trunk leak goes I hqave heard of a few and if I recall they sealed around the seals also and I know I had to tighten the top on mine because it didnt close tight on the seal.
I just turned the latch1 turn at a time until I couldnt lift the lid.

On our 86 Coleman Laramie, the floor was marine plywood. I asked the dealer the same question as to whether I should apply apply some sort of undercoating/sealer. He said that this would actually cause the wood to rot because the moisture becomes trapped in the wood. The wood has to "breathe". He assured me that he had never seen a Coleman floor rot in normal use that had been left untreated after it left the factory.

Whether what I've said still applies with the flooring materials used today, I don't know.

BTW- Is your floor really particle board, or Oriented Strand Board (OSB I think some folks refer to this as flake board)? I'd have to think it's OSB because particle board doesn't hold up to moisture at all.