i have some photos that i took whilst building the car back up, i will certainly post them up although it is not a simple fix! Your symptoms could have been a misfire aswell, i noticed as the wear was minimal on mine it had only achieved a loss of power but as the pulley wears more and more the car will become undriveable.
If Kia are going to replace the parts thats a good start, they will replace the bottom timing pulley, the crank shaft (hopefully) the large end bolt and id like to think a new timing belt and tensioner. Apparently a new crank is £900, the pulley is £20, bolt is £3, timing belt and tensioner is around £50 as a guide to what they will pay. The labour wont be cheap though!
id urge anyone with a sluggish car with missfire to stop driving immediately, the damage pulley will eventually give, and destroy the head and bend valves, break timing belt, it would be messy!
i will give a quick run though whats involved...
1. Remove drivers side wheel and plastic cover at the bottom of engine (4 bolts 10mm)
2. loosen air con/power steering belt, tensioner is on top of air con pump in mine
3. loosen alt/waterpump belt, tensioner can be accessed from the engine bay easy enough.
4. remove waterpump pulley (4 10mm bolts)
5. remove the large centre bolt on the bottom pulley (one faulty part)
6. remove the 4 bolts around the large centre bolt (10mm) and remove the two aux belt pulleys
7. remove the top and bottom timing belt covers, think theres around 8 10mm bolts that hold it on, the dipstick needs to come out of the sump to get at one, its held on with one bolt at the top on the head and simply pulls out.
8. Now you should be looking at the defective bottom pulley with the timing belt still in place, there is a brass toothed disk over it for the crank postion sensor that just pulls straight off although be gentle as this cant be out of shape! (all the pulleys etc and this brass plate ate held in the right place buy a locating pin in the defective pulley so can only go on one way)
9. Check the timing of the top cam pulley is lined up, there are timing marks on the pulley and on the head (should be at the 3 oclock position. loosen the timing belt tensioner just above the defective pulley and pull off (not the position of the spring that holds tension in it.
10.Remove the crank position sensor at the bottom beside the defective pulley (2 x 10mm bolts) you can now remove the spring for the tensioner.
11. The timing belt should now come off very easy
12. Have a feel of the bottom pulley, if it is defective it will move on the crankshaft without moving the shaft itself, this is the wear on the pulley, it should be loose enough to pull off in your hand, i will post pictures after of mine and the wear.
13. I thought my crank had escaped any wear as it looked fine and checked out with the micrometer.
14. ordered a new crank pulley(£20) and new 17mm centre bolt (£3)
15. Now the fun part, i slid the new pulley onto the crank, you guessed it, still slight movement side to side.

My crank must have worn slightly aswell.
If i was to put it back together, it would maybe cure it for 1000 miles but it would wear the new pulley just the same.
16. I thought and thought about what to do, i tried to put a shim in but to no avail.

This is why kia then replace the whole crank aswell or 'short block' as they call it. That comes with a large bill!
17. I decided to put a small splatter of weld on the crank end, then filed it down to fill the gap at one side, slide the pulley on as far as it would go, and knocked it the rest of the way, my god its tight now alright!

(this is a painstaking process as its very hard to get the file in the right place)
18. lined the new bottom pulley up with the timing mark (its at 1 oclock) theres a nick in the cog and a white mark. obviosly turn the engine by hand a few times to make sure timing is correct.
19. follow my instructions in reverse to build back up, and hey presto my little kia is back to narmal! woohoo! total time, id say took me around 4 hours, 1hr 30mins to strip, then a good hour getting the pulley on tight, and the rest building back up.
I hope this helps anyone who is thinking of doing the repair themselves if KIA refuse! Any questions just ask, and il try and get a few pictures up!
You can see the left picture below is the top pulley, the white mark at three oclock lines up with a mark on the head.
The centre picture is the defective pulley, notice the wear in the meant be two flat sides inside!
The right picture is the end of the crank where the pulley slides on and the flat sides mate together, the wear is not noticeable on this but it is enough to allow movement!
More picture later!