Sorry for my late reply. I saw your posting yesterday, but I was unable to answer at that time, and it just skipped from my mind later.
No, don't uninstall anything. Just enter the code and you are fine. You will be able to use both, the Garmin GPS20x USB receiver, or any other compatible 3rd party
USB GPS receiver.
I've done it, and it worked. (At least with the earlier version numbers it worked.)