It's unlikely that you'd make a mistake that would damage the microcontroller. The most likely failure modes are a key that never activates, or a key that is stuck activated, or a row/column that never activates, or a row/column that is stuck activated.

In the case of a broken row/column, if you can't find the problem visually, then you're stuck binary-searching your connections until you find where it is, but at least that's only O(log N) desoldering work.