This can be done easily with ethernet.
Please follow the instructions strictly.
To make it easier I want you to do this overnight so you can turn off all your current connection to the internet.
Just go to the airport fan in to the top right and turn airport off.
Get ethernet cable and connect the laptop to the TC lan port.. ie <-> ones.
Press and hold the reset on the TC for about 10sec. until the front led flashes rapidly.
Open the airport utility.. go to manual setup and change the wireless to off. (so other people around you cannot join your network of one).
Ignore all the errors.. they won't stop the backup working.
Go to the TM and reselect the backup target disk as the TC.
It should start after 2min and run through to completion.
That is it.. for a backup of many GB it might take a few hours.. so make sure the laptop has power plugged in and the sleep is off.. (on early ones I think this is needed but I am a late arrival to the scene).. sleep doesn't affect later OS.
Also, when I go to the airport utility a popup appears and tells me that the TC has been reset. It gives me two options:
1) Restore previous settings
2) Use default settings and save previous settings as a profile (Profile name: Recovered Settings)
Sorry I have so many questions - as you can tell I have no idea what I'm doing!