Dude, I was just about to do it. But there is ALOT to it. I mean ALOT, no I'm not being lazy here. There are a slew of parts you need. I can send you a link (have to find it at home) that details all your options and required parts. To do the job properly you have to pull the engine. You're looking at alot of money on parts alone. If you don't have your own lift and all necessary tools, you're gonna spend quite a bit at a shop. Not to mention, you have to alter the interior (center dash console, shifter, pedals, etc). After analyzing the whole situation, I determined that the next time my tranny blows I am just gonna buy the built auto tranny from Specialty Z.

Don't fuck up like I did, buy a manual.

The 300ZX auto tranny is pretty well built (although it can benefit from a better tranny cooler). But after aging or power mods, it will fail. I have blown 3 automatic trannies in the past year.
And trust me, it will be a bitch doing the conversion.
Much cheaper and less painful to buy a manual from the start.

If I could go back in time, I'd just import a Fairlady TT from Japan w/ manual tansmission(looked so zweet in Kill Bill).