Most of the drivers are already included in the distro. For your graphics card (NVIDIA), I believe you have to install the drivers (someone, please correct me if I'm wrong) which are already included in the repositories. You may have to install other drivers, but there should be plenty of tutorials on the interwebs to aid you with that.
That will depend on your needs. You'll need to change your keyboard layout the first time you run BT4 (in case you're living in a country other than USA). The control panel will also be a good place to adjust BT4 configurations to your needs/likes. Also check the HowTo section of the forums.
You'll probably not be able to inject, since it has a N wireless adapter, and being those relatively new, there's a chance BT4 doesn't have patched drivers. From my fast search on google, I believe 1215N uses a Atheros adapter, so if BT4 doesn't support it yet, chances are it will in a near future. But if you want to be sure, try to find out what the exact chipset is, then google "<chipset here>+injection", and read what others wrote about that subject.
As for the USB wireless adapter, I recommend the Alfa AWUS036H (do not confuse with AWUS036NH), but there are plenty of USB adapters you can use. Just be sure to check if it has injection capabilities or not (google "<chipset here>+injection") before buying.



