Oh, boy...be prepared to customize...not because you have to, but because it's fun.
I've had mine less than 2 years and it's on its third configuration.
The stock rear sight is more than adequate, though it is plastic (sorry, "polymer") for shooting accurately.
My advice would be to shoot it a bit in its stock configuration and keep doing research on options. That way, you'll determine what you want and need.
More advice, before you take it to the range, take it all apart and CLEAN it. That gunk on it is a preservative and not a lubricant. More than a few folks have taken them out of the box, loaded them up, shot them, and experienced problems. The problems arose from the "gunk".
Tearing it down also gets you familiar with how the rifle works.
Good luck with the new rifle.
Aqualung