Welcome aboard to both of ya!!
Chief, the hammer extension should be in the box in a white/clear plastic envelope like a packing list comes in, sticky on the back side. Whether you need it or not will depend on the scope and rings you choose, I prefer to not use it if I can avoid it, it increases lock time. The rail will already be mounted on the barrel, but I'd recommend you remove it, clean the loctite out of the holes down to bright shiny metal, then lap the rail to the barrel according to Perklo's instructions in the FAQ and remount it to eliminate any question about whether it was mounted properly from the factory or not, which has happened.
Triggers of late have been 3-4lbs, some have been as heavy as 5-8lbs though, just depends. A trigger in the 1½ -3lb range can easily be achieved with the info in the stickys and the FAQ if you're the DIY type, or the factory will get it to about 3½lbs if you ask when you ship your frame in for another barrel.
Lots of info in the stickys at the top of this list, I recommend you read em all, then ask questions that you still have..... if you have any!