You should be able to remove it, and re-activate your integrated video. Your repair shop should have disabled the integrated video via the bios setup... which would have removed the conflict with the card you installed.

To return to that setup, simply uninstall that video card and then boot into the BIOS and re-activate the integrated video. If you aren't comfortable doing that, then you might need to take it to a shop to have them do it for you. It's really not that hard, but I understand people are not comfortable messing with those things.

Not knowing your configuration, it should have been easy enough for them to configure your pc with both video cards functioning, and setting the priority for which is primary, secondary, etc. But I have never done that with integrated video before.

If they properly disabled the integrated video in the BIOS, then that shouldn't be a conflict with your new video card. Had you tried updating to the latest drivers versions to see if that helped with the problem? When you say it locked up, was it during any certain types of activities like 3D rendering / DirectX applications... or even when just browsing the Internet, etc?