Cracked and split CV boot, is it repairable?

The boot can replaced, but it doesn't make economic sense to do so, especially at the mileage you listed. New half shafts used to cost as much as $450.00, and professionally-rebuilt shafts cost around $150.00. Today new ones typically cost much less than $100.00. You don't get full of grease, the inner boot, which is just as old, gets replaced, along with the tired CV joints.

This photo shows what you get with the boot kit. I've done a lot of these while working for a very nice family-owned Chrysler dealership. As such, the wire ring with my blue arrow pointing to it is of the same design as on Chrysler products. Once you cut the boot away, have a helper hold the shaft in place in the transmission while you pull out on the axle stub shaft, and tap on the CV joint with a medium metal hammer. The wire ring will compress and the joint will pop off the shaft.

I have never been able to tap the joint back onto the shaft if I installed the new wire ring on the end of the shaft. I've always had to reuse the old ring, then the joints went on just fine. You can slide the entire shaft out of the transmission, then do the repairs on a workbench. I prefer to leave the shaft in the transmission to avoid the mess of about a quart of transmission fluid running out. You can also support the car so the side you're working on is a little higher, to prevent loss of fluid.

You can cut the old bands off the boot, or use a large side cutter for electrical work to grab the crimp and twist it back and forth. That will stretch it enough to allow it to slide off, and to be reused. Use the side cutter again to crimp it to tighten it. There's a special pliers for crimping these bands, but you can get by without it. That pliers presses the center of the crimp down so it doesn't hit anything as the shaft rotates. You can tap the crimp down while holding it squeezed with the side cutter to do the same thing.

Be careful when you reinstall the axle nut as most Nissans use a very fine thread that is easy to cross-thread. Run the nut on by hand first. Don't try to spin it on with air tools.

The only torque spec I can find is for that axle nut:

Wheel Bearing (Front)
Wheel bearing axial end play limit. 0.07 mm (0.0030 inch) or less
Wheel bearing lock nut tightening torque. 236 - 313 N m (24 - 31 kg-m, 174 - 230 ft. Lbs.)

As far as valuable information is concerned, these drawings are pretty disappointing, but that's all there is. If necessary, I can cut them into multiple drawings that I can enlarge for you.

No need to replace the other half shaft. This isn't like tires or socks and shoes where you want both sides to be the same so they're balanced for even control. Think of this like a dome light bulb. If it burns out, there's no advantage in replacing the headlight bulbs.

Also, replacing the entire shaft is the better choice when you factor in shop labor charges. It's less expensive for parts if you replace the boot yourself, but not if you have to pay someone else to do the work.

This video should help you change the boot out:

https://youtu.be/dqz72B02UdI

Let us know what happens and please upload pictures or videos of the problem.