I have been twisting wrenches for 32 years now, so I guess I am mechanically inclined!
The nissan transmission is a simple one. Compared to the old American ones I cut my teeth on ('70's stuff) it is a better design. It comes apart without much trouble, and you can see how everything works.
If you can follow directions, and use hand tools, you should be OK. You will need metric wrenches and a ratchet set, jackstands or ramps, snap ring pliers, and access to a small hydraulic press and some bearing splitters. It is not a bad job at all. I am just waiting on my bearing and seal kit and mine will be going back together.
Paint/Controls/Robotics Engineer by trade
1993 HB 2.4, 297K miles
1988 Suzuki Samurai 1.3
1995 Pathy, 3.0 5 speed.