The Pau'an mods are the closest you're going to be able to get to that (the Arkanians have tried the full age reset/extended lifespan thing before on themselves and it's never really panned out).
Believable. The problem in Star Wars is that no one seems to actually have found a way to natural extend lifespans over the past thousands of years and the few that do work are essentially powered by the dark side.
Plus genetic studies was not well known when Star Wars first came out so to prevent causing a massive retcon, most writers don't even bother with it. Especially since Star Wars scales to Science Fantasy to the extreme. Genetic studies are essentially in their infancy despite all the advance technology the setting has that should make research plausible.
Also we haven't bothered improving our medical science so that limits our possibilities. Given the complexity of the research, it could take several years just to make something decent and economical. Unless we find anything that could lead to a few shortcuts.