There are a lot of opinions and theories, as you've found out from the conflicting info you've gotten from the LFS. Some will say it interferes with the cycling process by removing DOC's that would otherwise feed the cycle. Some say run it to help the cycling process. Who really knows? No one has done comparative studies. One thing I do know: it does not make a big difference one way or the other. I've done it both ways, and know several others who have success doing it either way. May opinion, just run it. You'll need to break it in before it starts to work well, anyway, if it's new. Just keep the foam/water interface low, as new skimmers have a tendency to produce too much foam and may overflow.
I have noticed the foam and I'm trying to keep it out of the collection cup completely at the moment thanks for the help I'm bouncing all the info of someone in my family as well as he keeps marine but you have been a big help and I'm looking forward to stocking the tank