I transitioned from skateboarding to snowboarding, having the prior experience it wasn't a big jump and I got the hang of it fairly quick.
Long boarding IMO is more for the people who like to cruise around, granted I never long boarded before.
Skateboarding won't be awfully to hard to pick up, it's more about feet positioning and balance/stance then anything else, once you get that in check you should be fine. If you want to avoid having to kick push every two seconds, get decent ABEC 7 spec bearings for a smoother ride, 9 would be a bit too much for someone just starting out, 5 should be bare minimum.
If you won't be doing any tricking, more so just riding, a wider board, higher trucks and bigger wheels will accommodate that, a board 8 or more wide will do you, any less it's more a street board. If you were to get a skateboard, Plan B make really well constructed boards as I have mistreated mine and it's still going strong haha, and IMO Destructo make some good trucks.
I can't really think of anything else, I myself only been skateboarding for a few months now.
My snow surfer setup:
2012 153 Lib Tech Attack Banana
Ride Delta MVMNTs
Nike Kaiju Quickstrikes