I have the same issue with my 03 EX. My door lock works just fine, so looked it over and it turned out that the exterior handle broke off of the rod inside the door preventing it from unlatching. Pretty sure there's no release mechanism from the interior of the vehicle, so the whole door panel needs to be removed. I may start on mine tomorrow and I'll take some pics to post on here to show what you'll be looking at. Hopefully it will be some sort of help.

 

That would be great Justin! Let me know how it goes. I have a new handle for the hatch but the handle doesn't seem broken. When I turn the key I can feel it grab but then it slips off. Regardless, I can't change the handle without getting the hatch open first. Sure thought Kia would have installed a manual release as a safety feature. Good luck!

 

Didn't get a chance to look mine over today, but I'll get started tomorrow morning and take some pics and maybe a video too.

I did happen to find this posting if it helps any:

Help with my Rear tailgate latch on Sedona!

The rear tailgate latch on my 2003 Sedona will not open the darn door. I assume the linkage is broken or disconnected or something. Does anyone know how to access the area to see,or is there another way to open the tailgate?

www.kia-forums.com

 

I heard someone say to remove the light from the door panel and then you'll have a little wiggle room to get a large flathead screwdriver in there to pry the rods so it will open. Then from there the panel can be removed and just lube up those rods and make sure they are connected to the handles.
I'm about to get started working on mine, so I'll see what I can do and take some pics to post. I'll even shoot a small video and put it on youtube.