Ahoy and welcome. Yes, you'll discover muscles that you never knew you had, as well as soft and fragile bits.
The best initial advice is don't blow the kids' inheritance on an armoury of two-tones. You'll get a bit hit of adrenaline from both playing and purchases, but the classifieds are full of "never/barely skirmished" guns. Best to rent until you have a defence and are sure you'll stick with the hobby, or at least keep a rein on spending. Footwear, eye and face protection are the first priorities, shooty things come later.
Tips on playing are just: call your hits regardless of what's going on around you, and never take any of it too seriously, even if others are. It's just dress-up and hide-and-seek with toy guns at the end of the day.