How to replace Front door cable Hyundai i30 - Hyundai Cars & Trucks

You need an auto electrician with a pro grade scan tool. Or even an auto locksmith.

Boot is not supposed to open with door unlocking feature. Rear passenger door lock may be stuck. Does it work manually?

Switch is above pedal, remove cable plug, undo the locknut and remove, replace in opposite order!!

Don't worry I'm sure you will get the solution of your problem, just check the link I attached Hyundai I30

What is wrong with taking it in the shop?

Look at the throttle cable where it connects to the air horn and moves the shaft that controls the butterfly to let air in the manifold .
Even if it says its not adjustable usually is a small stop screw that you will have some control over how far the air inlet butterfly will come to a stop position .This will control the amount of intake air less air slower idle .
However you may have other issues .

I have a damaged Hyundai I30 door can I just replace the outside shell of the door ?