First thing is that they did not need to test "everything" to get it started. When you have 450 GeV protons in the ring, you dont need 7-8 Tesla magnetic field... So they got it started because they could and decided that they can test the high magnetic field setting later.
Second: The incident happened as they *were* testing it in a break from the low energy collisions schedule.
Third: It was more like 6 tons of helium...

But OK, you've got most of the story right.

You need to watch this: http://www.thedailyshow.com/watch/thu-april-30-2009/large-hadron-collider

No kidding. Eventually, we'll see a neutrino interaction even, I guess...

Well, here is an AC that clearly writes from the inside... Thanks!

Yes. It is used here as a unit of energy that *one* particle carries. Take a look at: http://en.wikipedia.org/wiki/Electron_volt The proton weighs 1GeV. 7TeV (Terra electron volts) which the LHC should run at, means that a poor proton will be so energetic that it will have 7000 times the energy that is it's mass. The higher energy a particle, the higher the magnetic field needs to be to curve it around the 27km ring. If the magnets can not handle the design current than that limits the magnetic field, which in turn limits the energy of the particles that you can accelerate. Incidentally, a 7TeV proton has about the same kinetic energy as a mosquito. But imagine that all the energy is being carried by *one* proton. Now, there are 100 billion protons in a beam bunch and 2000 of these bunches running around the LHC, according to the design and in the end, the total kinetic energy comes close to that of an aircraft carrier going at some reasonable speed, I am told... ps. I am not the AC who posted earlier.

True. But it is the *scale* that matters. ~27km long cryogenic line... has that been done before? For example, many off the shelf cryogenics components were not available before the LHC came along... So much was custom made. And now many components became off the shelf with the R&D money that CERN injected into the industry and so MRI machines and other cryogenics systems are becoming cheaper for those who want to use/study them.

About right... There are 1232 dipole magnets in total.