Darren2627,
Refer to the attached picture for the dimensions.
There is no need to cut the IGN +12V wire off the key assembly, you just tap it.
The way you are asking me these questions, I strongly suggest you just bring this button to an accessories shop to get it done. Without wiring knowledge and the correct tools to slice wires, the job would be rather difficult. Furthermore, you may need to drill a hole in your 'desired' panel to get the button go through as in my first post picture. If you have further questions, kindly call me at 016.4539687 It will be better for me to explain verbally as I am poor in explaining via text.