You'll need to renew your license and get the IDP from JPJ. I'd do them both at JPJ straight away since your CDL is expiring.

IDP requires you to have a valid physical drivers license.

Last I check, JPJ requires proof of planning to drive overseas (i.e. travel plans, flight tickets, etc.) in order to issue you the physical drivers license. Not sure if it's still required since you will be applying for IDP at the same time anyways.

Have fun driving in South Korea and drive safe! I always get confused when back in KL after driving on the opposite side road for too long lol