And you have to make a bracket for the cable to the gearbox.

But yes, pretty much as simple as that.

As long as you have the cable adjusted correctly you can drive the car without sequential working you will just have PRND only.

But the electronics get the SSS working?

The PRND is mechanical (i.e. gears selected by the cable) and the SSS is all electronic (i.e. gears are selected by the transmission module)... Is this right?

Is the bracket for the cable difficult?

look in my gallery to see my bracket, was the first one I knocked up quickly from computer case!

Yes
SSS = electronic
PRND = mechanical

P.S. I drove around for about 2 weeks with just PRND while electronics got sorted.

In most autos first gear is close to second gear in a manual, because the torque converter allows this. So once you're up and moving a 4spd auto has similar gearing to a 5spd manual.

On another point, one reason to have a car stay in the gear that is selected, is in the case of starting off on ice, where you might like to start in second gear in an auto, and not have it drop down to first.