1) Raise the rear of the car using a jack and support it under the frame using a set of jack stands. Remove the rear wheels using a lug wrench to remove the lug nuts and set them aside.

2) Locate and remove the two brake caliper mounting bolts on the back of the caliper. Remove the bolts using a ratchet and socket then pull the brake caliper off the mounting bracket.

3) Remove the brake rotor from the hub. Pull straight out on the rotor and slide it off the wheel studs. Set the rotor aside in a safe spot so that it does not become damaged.

4) Locate the four mounting bolts that secure the hub. Remove the bolts using a wrench or socket and ratchet. Remove the hub by pulling it straight out of the knuckle. You may need to encourage the hub to come out with a dead blow hammer if it is seized into the knuckle.

5) Lubricate the axle knuckle with a light coating of bearing grease. Install the new hub into the knuckle, making sure that it completely seated in the hole. Apply a small amount of thread locking compound to the threads on the hub mounting bolts and reinstall them. Torque the bolts to 70 foot-pounds with your torque wrench.

6) Slide the rotor back onto the wheel studs and spin one lug nut onto one wheel stud to hold it in place. Reinstall the the brake caliper onto the caliper mounting bracket and install the mounting bolts. Torque the mounting bolts to 30 foot-pounds with a torque wrench.

7) Remove the lug nut holding the rotor and slide the wheel onto the car. Install the lug nuts and tighten them until they are snug with a lug wrench. Remove the jack stands from under the car and use the jack to lower the car to the ground. Tighten the lug nuts with your lug wrench and test drive the car.

Check with the many on-line auto parts sources, such as; www.autopartswarehouse.com or www.rockauto.com. They (RockAuto) list the rear wheel bearings (inner and outer) from around $10.25 each for your vehicle. Remember to always replace the hub / wheel bearing assemblies in pairs or in axle sets (both sides) - due to age / mileage / wear considerations.

Most likely this would be the ABS sensor wire. You will need to install an ABS sensor which has the new wire lead.
Try the many on-line auto parts sources, such as; www.autopartswarehouse.com or www.rockauto.com for the replacement parts. For example, they (RockAuto) list the ABS sensor from around $18.70 for your vehicle.

Yes there is a difference, check the various parts listing for the rear axle bearings at these on-line parts sources, such as; www.autopartswarehouse.com, www.rockauto.com, or www.partsgeek.com - to list a few.

does your interior lights work?

Check fuse # 71 and if it is good, turn on the headlights and see if fuse # 71 has battery voltage on both sides of the fuse and update the post.

First thing you should do in this case is check your brake fluid. It can cause this symptom

They're supposed to come on and stay on when the system is no longer online. What you need to do is have the codes scanned. usually a VSS sensor or broken wire somewhere is the culprit.

The brake fluid may be leaking into the power brake vacuum booster - just behind the master cylinder. Check the many on-line parts sources;such as www.RockAuto.com, www.autopartswarehouse.com, or www.autopartsfair.com - for the replacement parts.

WARNING
Clean, high quality brake fluid is essential to the safe and proper operation of the brake system. You should always buy the highest quality brake fluid that is available. If the brake fluid becomes contaminated, drain and flush the system, then refill the master cylinder with new fluid. Never reuse any brake fluid. Any brake fluid that is removed from the system should be discarded. Also, do not allow any brake fluid to come in contact with a painted surface; it will damage the paint.
When any part of the hydraulic system has been disconnected for repair or replacement, air may get into the lines and cause spongy pedal action (because air can be compressed and brake fluid cannot). To correct this condition, it is necessary to bleed the hydraulic system so to be sure all air is purged.

When bleeding the brake system, bleed one brake cylinder at a time, in the order given.

For vehicles without anti-lock brakes (ABS):
Right rear
Left front
Left rear
Right front
For vehicles with anti-lock brakes (ABS):

Left front
Right front
Left rear
Right rear
ALWAYS keep the master cylinder reservoir filled with brake fluid during the bleeding operation. Do not allow the reservoir to run dry. Never use brake fluid that has been drained from the hydraulic system, no matter how clean it is.
For more information......... http://www.autozone.com/.../...rGuideContent.jsp

Check the power brake vacuum booster.
The brake booster gets the engine vacuum with the assistance of a rubber hose that comes from the intake manifold. Then the vacuum is used to increase the pressure that's applied to the pedal, making it much easier to stop the vehicle without having to stomp on the brakes.

check your brakes.

Confirm that the bulbs are not faulty. If they are okay, check your fuse box. Your manufacturer’s manual should tell you whether your tow vehicle has fuses for trailer circuits. Rust or corrosion also causes the lamp to loose connection. There could also be a problem with the wire that’s from the lamp to the trailer connector. Visit a mechanic for a check up.
http://4wheelonline.com/towing/Reese.177038

A professional has to attempt to bleed this brake system I believe. Proportioning valves rarely fail, you did not need a new master cylinder. Can you be certain that there are no rusted through brake lines leaking when you pump up the pedal?

its possible the rear calipers are frozen.

Maybe this will help- http://www.fixya.com/cars/t591760-xterra_2000_abs_light

Check the fuses and relays first.