1. I'd recommend taking a look at this link for that mesh: http://www.feral-heart.com/index.php?option=com_jfusion&Itemid=2&jfile=index.php&topic=47151.0 (http://www.feral-heart.com/index.php?option=com_jfusion&Itemid=2&jfile=index.php&topic=47151.0)
Basically you'd want to open it's texture in Gimp or Photoshop (after placing all of the files in the .zip/.rar into Feralheart\media\objects\my_objects) and simply edit it. Then save/export it to the same file and see how it works in-game. If you want to make a different sign everytime you place it in your map, make a copy of all of the files, go into the materal file (open with notepad), and you'll see a line that says somethig similar to "texture texturehere.png/jpg. Edit that "texturehere" to "texturehere2," rename the texture file/image, and then edit it.
2. Here's a great video that will help you with it!
http://www.youtube.com/watch?v=0viVTiaECPc (http://www.youtube.com/watch?v=0viVTiaECPc)
No problem! ^_^ If you need any more help feel free to ask here, or PM me.