1 - You have to open the script using the basic Notepad and save the script as ANSI. So you will be able to use other characters.
2 - After changing the lines on the scripts you have to type @reloadscript to reload the changes.
3 - You have to change all "Warper" in the duplicated NPCs to Teletransportador at the end of your script.
4 - If you mean the sprite you can find it in your data.grf. The items are already added in item_db, if you want to add differents items, you can find a bunch of grf downloading privates servers and copying their grf if they are not enncrypted.