Congrats on the NPAP- it's a terrific rifle. No gremlins to speak of, but you may experience some cheek slap due to the stock's high comb. Not everyone experiences it (depends on how you shoulder the rifle) and there are ways to work around it if you do. Be aware when buying certain parts that you may need to seek out yugo-specific items.
Before firing your rifle, make sure to clean it thoroughly as there will likely be metal shavings hiding somewhere (even if you don't see them) from when Century opened-up the mag well. You may also want to spend some time working the safety and gas-tube lever as they'll be very tight. If they don't loosen up, you can gently run a metal file along the nub on the underside of each to take a small amount of material off. Be conservative. I wouldn't start messing with the trigger unless you find a problem with yours. The G2 trigger works very well out of the box so most don't need polishing.
Since this is your first AK, you'll get a crash course in surplus mags. There is a great deal of variance between milsurp mags even though they're all "in spec." Some may be tight in your rifle, some may be loose. That's not an issue, that's just the way it is. Tighter mags may require some light filing to fit, but remember: file the magazine, not the rifle!