The preview button in the CK refuses to work ... The first of the links I posted walks you through what sound file formats to put where ... but - as far as I know - you must listen to them outside the CK (or in the game), the CK won't let you (bug, as far as I know).
As for your code: Are you making it hard for yourself?
1. Do you know which two stools are involved at Design Time? I mean, can you go and select them, in a scene, in the CK? (or can they be any of the stools in any of the Inns?)
If you can select the stools, then you can do what you want much more easily. If it can be any stool, anywhere, then your scripts are taking the right approach ... but may not be doing exactly what you think they are doing
The last bit of the script looks a little odd compared to the rest ... The top bit is basically figuring out whether the player is sitting on a particular stool, and whether a certain quest is at the right stage. If both of those are true, then it appears to be assigning another stool to be one that an NPC should go to sit on (but it does not actually go and make them sit ... maybe you have another script that is doing that?)
The bottom bit of the script then checks the stage of FirstQuest (which you assigned in Properties) and if it is at MORE THAN 20, it sets this second quest (the one currently running the commands) to stage 10. What happens then depends on what is happening in Stage10
Can you break down what is going on in your quests, what is working and what is not (and yeah, that might be a long post

); but it is difficult for me to figure from what is already posted here ... I don't mean the scripts; just what is supposed to be happening ...