Yes there's a knack to it. You turn it upside down, you have all 4 springs poking out the side, one at a time you raise the housing where the spring is and poke it in, then the next, then the next etc.

It's easy, it took me 2 maybe 3 attempts. One spring is harder than the others due to the position of the cable, do this one first.

Just have a good look at things and you'll see it's do-able.

EDIT: forgot to say, when you turn it upside down, the weight is on the shaft at the bottom, this pushes the housing up inside, making it easier. So be sure that you're balancing the weight on the central shaft, this pushes the assembly up on the inside and makes it all possible.

Somebody needs to take some pics and do a guide, it'll save so many people so much money. I have a starter to do yet, as my spare, I'll take pics when I do it, later this week perhaps.