Kia doesn't publish instructions for servicing JUST the latch assembly for the sliding door. They only have instructions for disassembling the ENTIRE door.
Basicly, this is what you need to do.
Remove the screws and the door finish panel. Part of it simply "clips" into place. Make sure all of the screws are removed before pulling on the panel to get the clips to let go. You will have to be inside the vehicle with the door closed to access some of the screws. The others can be accessed with the door partially open. The door will have to be open to get to the screws at the bottom of the door.
Remove 3 bolts securing the inner door handle.
Carefully peel the door screen (plastic film) from the door.
There should be 3 bolts securing the latch assembly to the door.
Release the clips securing the outer door handle linkage to the latch assembly.
Remove the latch assembly.
Reverse procedure to install.
There is also a Technical Service Bulletin (TSB) published by Kia that addresses sliding doors that are hard to open or close. It covers all the ADJUSTMENTS
on the door that can cause these types of problems. The bulletin itself has lots of pictures and instructions about how to check for the actual CAUSE
of the symptom and how to make adjustments to correct it. It is too large to post a copy here. You may try going by your Kia dealer to see if they will print a copy for you. If not, you can access the information by subscribing to AllData DIY
for a small fee. (around $27/year)
It is Bulletin Number TT820405-001