I called Kinro.com directly. The RV industry is still starving and the manufactures will sell to anyone.
As far as cutting into your trailer, I used two methods: 1) die grinder to cut the outside skin 2) strong SawZall to cut studs.
I'm not afraid to try to do anything (not always a good thing), but take your time and you'll do fine. It gets easy after the first cut.