LP BBQ grill. Deck has propane outlet for grill. Can just hook BBQ up to this? Who to call to hook up?

Normally it is a screw type connection. I am a bit curious where the feed is for the propane - unless you use propane for heating and/or cooking. The connection itself is easy, even if you need to install an extension to reach the grill. All connections should be tight (do not over-tighten) and can be tested with ordinary bubble water (yes, the kind you buy for kids). Pour the bubble water on the connection. If you do not see any bubbles then there are no leaks.