tank sticker
I would not remove the tank sticker and it is very hard to damage it other than time dependent deterioration (it lasted this long without you) and look how hard it is to even see it when the tank is in the car. However, I understand the need to preserve the identity of the car. If you must, drop the tank and take pictures of the tank sticker in place, if you remove it (the sticker) you probably will damage it and also it is no longer in place on the tank. An extreme case would be to remove the tank and replace with aftermarket but I see this as almost absurd. These cars were meant to be driven and enjoyed, the verification of the true identity of all components has undeniable value but I feel that part of the allure is these little in place time capsule artifacts.
If its falling off then you probably could remove it safely but otherwise I would leave well enough alone and if necessary place some type of protective covering over it on the tank and then reinstall the tank. This is probably not what you wanted to hear but its only my opinion and you know what they say about opinions. All the best.
Gerry