Technically you didn't kill it or even 'brick' it. You just temporarily disabled it by 'standard' formatting it using Windows, that's actually an easy fix which is no doubt why they were happy to do it. Nice of them to accommodate you regardless and good PR.

About your maps 'problem', just to add to what Pungente has wisely told you: The standard advice is to NEVER have more than one map enabled covering the same area. The problems may never be apparent or they maybe will occur quickly and catastrophically when you are in the middle of a very busy peak hours in an unfamiliar city. I once saw an AU 1390 which had on it both a current version of Navteq [HERE] and the previous version of Sensis CNNTs. I was horrified because the guy had both enabled. He then told me it had been like that on a trip from Perth WA to the East Coast and never missed a beat. When I told him that even though he'd driven right across Australia without a problem it could still freeze or reboot or worse if he drove a route thru a local suburb on B roads and side-streets on the way to the next suburb he didn't believe me. But that's possible. Often one map will cover the other/s as you've found even though the priority is the same [30 with CNs].

Safe option is tick only one at a time if they cover the same area.