The "chicken Farmer" is right (if you explore the forum, you'll see why we call him the "Chicken Farmer"
Hint: read the "Picking up Chicks" thread he started ).
I've had gun dealers/salesperson, tell me everything to 1). "you don't need to clean it, it's ready to go", 2) "you just need to run a bore snake through it first, then you can shoot it", to 3) "you should clean it before shooting it".
I always clean my guns before firing for the first time. After reading the manual, I follow the instructions to disassemble/reassemble the firearm (sometimes additionally watching uTube videos especially for my old WWII rifles that I don't have a manual for). Breaking them down first allows me to see how they came from the factory, before I clean them. Some have a light film of oil (fine), some dry, almost all I get some residue on the patches I run through the barrel (probably from their test firing). I one time broke down my Stoeger semi-auto shotgun, and it was packed (and I mean packed) with grease, which I would have preferred not to shoot in that condition if I could prevent it. So I came to the decision, to always read the manuals before attempting to shoot it for the first time, and by disassembling/reassembling after cleaning, I received a better understanding on the operation of that firearm.
Like 10mmLife mentioned, welcome to the forum, congrats on the new firearm (I second your success in finding 9mm ammo), and much luck with your new firearm.