Its a simple 2 wire set-up so there is no chance of error if you do it carefully. No extra engineering required. However during installation Clock spring need to handle carefully and if you remove steering, be careful and remove and reinstall in centre position otherwise clock spring will not sync back with steering rotation and can be damage. Don't forget to disconnect negative terminal from battery.
I will not comment on price and genuine/non genuine.
There are 2 type of CD/DVD/Navi units are available in market or OEMs,
1- With learning mode ( Mostly this type available in Chinese navi, You can install any controls with any resistor value. After installation you may program the keys as you want and there is no key restriction i.e. you may program vol up as vol down or menu key can be program as mute/ power off. New Altis Navi and tracking world new Civic navi is also belong to this group. Both players can be used with 3 wire set-up and both are quad navi controls like you find in New Honda Civic.)
2- Without learning mode (In this group we have Japanese manufacturers like Kenwood, Pioneer, Sony etc. They need specific resistor value for specific function key. Some of their models also support 3 wire set-up and quad navi controls like you find in New Honda Civic.)
For both set-up you need to change the resistors values or install adaptor. Till now there is no way to "just plug and play" the used Japanese controls (came in imported cars/Kabari market available with Japan fitted navi or DVD)