It's difficult. The standard way in frogs is to just keep injecting them until the altered cells outnumber the regular ones. You wouldn't have to change them al

It's difficult. The standard way in frogs is to just keep injecting them until the altered cells outnumber the regular ones. You wouldn't have to change them all though, often genetic diseases are confined to a particular tissue. There are also theories around using a live virus to carry the genetic material, theoretically a virus like that could leave behind the desired mutation as it replicates through the body's cells. Promising mechanism, though I don't know of anyone who's pulled it off.