Only place i know is Lego land it has every Lego batman decals
In the lego store at mall of america.
saber scorpian.com
I don't know but you can find it at Minifigscustoms.com under designs
brickshelf flickr and images
You can probably find some different types of decals at sabre scorpion or you could just get the brickforge ODST armour which already has decals applied to it
i believe you can find them on a blog called brick shelf
go to google then type dbz lego decals then click images
This will depend on what kind of decals. The decals made by the Lego group is quite easy yo remove and you can do that with your nails. But custom decals are tricky. Most of the time they are perm, so you will have to get a scraping tool to get it off, therefore, damaging your Lego. That's why custom decals are discouraged by traditionalist.
No
I would start my search at E-bay.
Mostly, decals are free, but higher quality decals have to be bought, or printed on plastic., as standard printing stickers are not waterproof, with low durability. Anything printed using printer stickersheets is not worth the money. Go to saberscorpion.com for quality decals for a start, or browse around mocpages.com for free templates.