you can get lsd 2 ways. 1 is to find the appropriate lsd tranny and swap tranny. The other is to find a lsd tranny and take it out and stuff it in your tranny.
Either way, it only takes as long as a clutch job.
The axles themselves aren't different. Theres something that presses onto the axles for abs and lsd. When I replaced my axle I took it down there... he pulled one off a shelf (like he would have an lsd axle in stock) and took a couple of widgets off of my old axle and pressed them onto the new one. I really wish I would have asked him more about it at the time.
To get an LSD tranny you need to find a tranny with a model # ending in "V". You will also need different (not just new) output shaft seals.