Reactor=God Smiling upon animators
Reactor is probably the greatest thing to happen to 3ds max ever, it allowed realistic physics simulations with only a couple clicks of the mouse (okay it was a little more then that, but it is darn easy). My advice would be to go through the tutorial book that came with max 5, it will take you about 10 hours, but then you'll be a reactor pro, and you'll wonder how you lived without it. Reactor ROCKS!!!!!!!!!!!!!!!
AS for a real world scale of a pen being 8 inches, that doesn't matter. You make a real-world scale. Reactor only reacts with the sizes of the object, and just treats every piece as a chuck of geometry. Will you get different effects if the pen is 100 units big as opposed to 50 units big? Possibly, but only if everything else isn't to scale. Meaning if you were to make a robot crashing through a wall of bins, and the robot was as big as the ramp, of course you get different results, then if the robot was regular size. With reactor just keep in mind: Proportion. And you'll be okay. And when you get really good with reactor, you can have some crazy fun with water
. You'll see what I'm talking about.
And no matter what, if you are somewhat skilled with reactor, it will always look better and it will be easier and less time-consuming then animating it by hand. Unless your name is reisser from team 103, and you have some sort of ungodly ability to animate everything by hand
Hope that helped.