Yeppers ... lot of reading indeed. Congrats on the purchase.
I'll try to give you a $0.50 overview.
In P mode, the camera will go for shutter speed first, to help eliminate camera shake, then it'll play with aperatures to increase you depth of field. Or, as light diminishes the reverse, aperature goes first, so you'll lose depth of field, then shutter speed, it will try to maintain a recreprical of your focal length, ie. 70mm = 1/100 sec., as I said ... it will try...
a mode and s mode speak for themselves, and m mode will allow you to set your combination as you see fit.
ISO ... well let's see here ... the D100 does pretty good up until about ISO 800 then noise becomes a factor, but depending on how full a frame you'll end up using ISO 200 may produce too much noise.
You'll have to develope a technique, I prefer to hand hold and use strobes, others prefer slow shutter speeds and use a tripod, it's all up to the style that you'll develope as you create with your own personal taste.
The flash will help overcome the troublesome white balance issues, but I usually start with my white balance set to fluorescent +3, without a flash, shoot ... could be -3, been a while ... forgot.
Let's see some pics.
