The leather on older cameras was secured with shellac, which is soluble in alcohol. This can be obtained at any paint supply. Vinyl coverings on later cameras are secured with a variety of contact adhesives, which are soluble in such things as MEK or laquer thinner. You have to be more careful with these as they can damage plastic parts.
I would peel off all I can, and try the citrus-based solvent as Nick says. Its very mild and shouldn't hurt anything - but don't get in the mechanism. If that doesn't work, I would try the alcohol, followed by naptha, followed by MEK. Hopefully you don't have to go that far.