You can reuse the bearings. Sometimes it's nice to clean them out and regrease them, but also not a requirement. Just be sure to keep debris out of the area when you swap the rotor.
You can do the work at home, but without a suitable adapter to check the initial lock tightening torque before backing it off, you have to rely on feeling things out. In the end, it's not the torque that matters as much as it ensuring that you've backed-off the nut to both allow for free rotation, but not made it too loose on the bearings. You may also need to be creative when it comes to removing and tightening the lock nut. I use a small drift and a hammer to do both; hasn't failed me before.
And if you don't have the Factory Service Manual (FSM) handy, download things here:
https://www.nicoclub.com/nissan-service-manuals. Info you need for the hub work is in the Front and Rear Axle (AX) chapter; Brake System (BR) is a the other chapter you'll want.