After 8 years of NL cash I'm making the move to HU SnG or Spins, I haven't yet decided which.

The common wisdom back in 2008 was that ICM is the most important  concept to get to grips with before you can win consistantly.

I spent an afternoon at the weekend Googling around and I saw this

It's two years out of date now. Can anybody help me with what might have changed over the years since I last played any tourny poker? Is ICM still viewed exactly the same as it always was? Would this be a good primer for me?

If I wanted to study two concepts at the same time, what would be the next most important?

Many thanks