I don't want to sound stupid but I keep seeing references to NISMO... What is it and where do I get these?

Nismo, you can find at the dealership if you wanted to. I would go find another brand that you like better ... and not pay for the NISMO name.

It's the performance division of Nissan. Nissan International Motorsports (Nismo). If you're one of those ppl that likes to keep their mods factory, there you go.

http://www.courtesyparts.com/nismo/xterra/index.html

Try one of these to get the knob off...You can add a piece of pipe for added leverage. Home Depot sells Rigid Brand ones in metal also.
Clicky

I used duct tape and a 24" pipe wrench to remove mine.

does anyone know what size the thread is on the 5spd?

I believe that the thread is 10mm x 1.25 pitch.

I that is what it is for the t-case, and I'm fairly certain that's the case for the tranny.

thanks Cyclemut!