Hey fellas sorry for the noob question but I'm getting the occasional grinding gears in the mornings and hard shifts. I was planning on getting maybe some gear lubricant but after reading a couple of threads i'm completely lost. Which one do I actually need gear oil, gear lube, clutch fluid?? Like I said i'm a total noob when it comes to stuff under the hood so bare with me. I have a 2003 6mt with about 75,000 miles so i'm about to go in for an oil change and figured they could do the other thing as well.

thats pretty neat thanks. I guess i'll be heading out to autozone to pick those up!

The one this guy is recommending is 75w90 but when I called the dealership they told me to get 85w90..????

Here's a link about the product he has listed. It says it replaces 75w90 and 85w90 products. If you want to stick strictly with 85w90 you can contact your local Nissan or Infiniti dealer to see if they have it in stock.
https://www.amsoil.com/storefront/svg.aspx

i'm probably just going to stick with the 85w90. Thanks though! also how many quarts do I need for the differential change?

Buy 2 quarts and 4 quarts for the MT (if you decide to change that as well). If you do it yourself, you'll need a 10mm hex bit driver, torque wrench and hand pump. Otherwise, just make sure where ever you go (if other than an infiniti dealership) they have the torque specs for the drain and fill plugs.

BTW, use only GL4 for the MT and GL5 for the diff.

You should also go to this link and download the PDF of the FSM as well

https://g35driver.com/forums/faq-diy/200667-factory-service-manuals.html