That's a whole new one on me. I've been on this forum for a while now, and haven't run across any discussion at all about replacing a phone camera lens, so I'm afraid you're in uncharted territory.
Outside of the unknowns involved in the actual replacement, the other place you're going to have trouble is in finding a replacement lens. Nobody but nobody is selling those; the best you're going to find is getting another camera to salvage the lens from. Of course, if you've got another camera, then you've just negated your whole premise of not wanting to replace the whole camera.
It would definitely be an interesting repair to see, and documenting it with a new guide would be awesome if you're so inclined.