The gum disease can be treated in one to two appointments fairly easily,then you could do the veneers as soon as your pockets shrink. The dentist will tell you when this occurs. Dont let a dentist do the veneers first then treat the disease after.
A traditional dental veneer can be removed and replaced with another dental veneer, but a true return to the original dentition is not able to be achieved.
A feldspathic or "ultra-thin" porcelain can be placed over the existing tooth and can be removed. That being said, a return to the...
If the front of your tooth is thin and there is enough enamel then you can get veneers.
If the back of your tooth is damaged and thin then I would recommend a crown to cover your entire tooth.