I have a 2005 Nissan Xterra the past 2 weeks I've noticed the engine/transmission//or rear end bogging down.......it happens when I slow from a steady speed! Please help!

SOURCE: Front End Noise in 2005 Nissan, Maxima

it would not hurt to check rear tire wear due to misalignment
cupped tires will cause a faulty bearing type noise or humming.

SOURCE: Ford Focus Engine problem

have you tried having your fuel injectors cleaned on it. the engine might not be getting enough gas at take off. it might also be that your gas tank fuel pump or the other fuel pump going bad

SOURCE: remeove rear combination tail light cover 2006 Nissan XTERRA

I just changed out a tailight on my 2000 Nissan Xterra, so I assume it may be similar. You have to pop the plastic strip which runs across the back. There are pop rivits in it.

SOURCE: 2002 Nissan Xterra drivers power window wont roll down

Quite possibly yes...I would first check any relays and/or fuses just in case.  A few dollars for a fuse or relay is much cheeper than say $100.00 and a few hours of labor.  
You can purchase just the window motors from any major auto parts stores.  You can also purchase the window motor with the regulator.  The regulator is kind of like a rope and pulley system to lift the window up and down and the motor is attached to this assembly.  It is a little more expensive but I would change both.  I always change both just in case the regulator is bad and it isn't the motor.  You will have to remove the plastic interior of the door in order to change either the motor or the motor/regulator assembly.

Any questions, feel free to ask!

SOURCE: 2000 Dodge Caravan transmission issue

have the car scanned for computer codes in the transmission section,most big name auto parts stores will do this for little or no charge, make sure they look for transmission codes. when you get these get back to me and we'll go from there,please rate my fix as i strive to be the best,don't leave negative feedback, just get back to me