Fixing Realtek networking on Ubuntu 11.04 (Natty Narwhal)

Tonight I made the mistake of upgrading my primary home work computer to Ubuntu 11.04 in the middle of a crunch period at work.  I'd found the perfect time for it, I thought; start the upgrade and get the kids to bed while it runs (monitoring it every now and then).  Once the kids are tucked in, I reboot the box.  So what happens?  

Boom! no network.  dmesg says 

r8169 0000:02:00.0: eth0: unable to apply firmware patch
r8169 0000:02:00.0: eth0: link down
ADDRCONF(NETDEV_UP): eth0: link is not ready

Ouchie; I, like, uhm, really need net access for work.

I'll elide the approximately four hours of increasingly panicky fiddling and Googling that occurred at this point; I feel my blood pressure rising just thinking about it.

End of story:  Check which Realtek chipset you have using lspci. Grab the appropriate proprietary driver, r8168 or r8169 (hope for the 8168, the 8169 driver doesn't even compile without the changes this guy details; luckily I have an 8168) and install it.  I have net again!

Now to do what I originally booted the box for.