How much does the sequential shifter cost ?

The shifters are 2650 Australian dollars.

Will I need to modify my gearbox ?

The shifter bolts straight on, the hardest thing you will have to do is change the offset lever which is the part that is held on the selector shaft with a roll pin.

Will i have to use the clutch ?

If you have a gearbox that still has synchro internals you will still have to clutch if you have a faceplate style gearbox you wont but will need supporting electronics to make this work well.

Why have the shifters taken so long to be completed ?

We tried to make the shifter locally.This was a mistake as 2 different places we went to just gave us the " it will be finished next week " line evey time and dragged this out over a year even though they had agreed to set delivery time before starting the job.

Will it speed up my shifts ?

Yes, the shifter dramatically improves shifts entirely through making it easier to for the driver to interact with the gearbox.