Yeah - unless something goes wrong
. If your onboard graphics is functioning properly, you should be fine. If you are in any way nervous, don't disable the onboard, but install the card atop that. The onboard should switch automatically to the card - either that or you may have to manually switch it in the bios (either way it is do-able). But, you don't HAVE to fully disable your intergrated graphics when installing an actual video card. You can just check in the system when you install the GS, as to whether the computer is using it or not.
Like, I am running with my onboard sound enabled even though I am using a seperate soundcard. The card simply overrides the onboard, disabling it.
What kind of computer do you have? Is it stock or custom built? Are you running it with intergrated video at the moment with no issues?