Just leave it in man.

Shouldent cause a problem, and you might loose some performance if its in dual channel mode anyway.

Load up a massive scene with hair (as its really ram intensive)and then render it with mental ray and have a look at the task manager, that should tell you how much ram your using.

I didnt know that graphics ram was included as I thought it was a sepperate part of the machine, other wise why dosent it show it as a processor too?