Yes, you can put a dedicated graphics card and use it exclusively for driving monitors and stuff.
Your motherboard's graphics will not be used anymore if you are using dedicated graphics. You may or may not need to disable your Motherboard's graphics from the BIOS though, but that's about it, and is a fairly easy process.
Just install a graphics card and start using it, 9 times out of 10 it should not be a problem and OS should automatically select the one. If you have problems then post back in Toms, someone should be able to help you out.
You can use either motherboard or dedicated at a time. You cannot pair them together unlike AMD APUs.
I hope that answers the question. Been some time since I've posted in toms. Ask back if you...