I went to it last year. It was not only the first time I've been to the Pomona, it was the first time I've ever gone to any such gathering. Yes you can park/camp on site, however you must contact FMCA to reserve a spot and get an arrival time. Last year there was plenty of room. I thought it was very well organized.
I don't know if suppliers and manufacturers do service there, as I didn't see any of that. There was a great selection of all makes and models of motorhomes.
Peter - Doctor of Mixology