1-how easy is it to put the skin? any bubbles appeared? also...is it easy to remove? how well do both ipod and paint resist scratches?
It was easy to apply. No bubbles that couldn't easily be worked out. I had a DecalGirl skin on my Nintendo DS and it was easy to remove, left no residue and did not damage the finish.
2-does it have holes for all accesories? (i.e: earphone, pc connection) silly quetion, but necessary
Yep, skin does not go all the way around the sides.
3-Have you noticed a decrease in the quality of the speakers and or wi-fi connection? how about heating? does it heat more than usual?
Speaker sounds the same, wi-fi is the same, heat is the same.
5-how bigger it becomes? that is: I am not going to put inside another protective case, but could it fit into the docking accessories?
It's a sticker, so the iPod is still thin.