Can one disable the IPv6 stack on Debian Linux, especially Wheezy? If so how do I know if it's disabled on a system?
Yes, you can:
echo net.ipv6.conf.all.disable_ipv6=1 > /etc/sysctl.d/disableipv6.conf sysctl --system
But you might need to do several other things, as described in the related article in the Debian wiki. The description for squeeze should still be valid for Wheezy.