Does the differential have different fluid from the tranny, can we replace it ourselves(read; is it easy).

 

Yes. 75w-90 GEAR LUBE for the diff, normal 75w-90 for the trans

 

Are we talking auto or stick here? I know on the stick its all one unit. On the auto, there may be a second unit but I dunno..

 

I have a 5 spd - how do you drain/refill the diff. I have never even heard anyone discuss this before.

 

There should be a drain plug and fill plug on the diff. Crawl under there and look around for it. The drain plug will be located lower than the fill plug (or should be!). I have no clue what it looks like on the Maxima so I'm just going by how other cars are setup.