Gearbox must be a T40 / T50 to fit a 4AGE, not sure how to identify them, just ask at a wreckers or get one when you get the engine that definatly suits it.
Clutch pedal box is from the clutch pedal, mounted through the firewall to your Clutch master cylinder
Tailshaft runs from the gearbox to the diff
Most of the stuff should be a direct bolt in, may need to play around a bit to get the clutch pedal box in, but apart from that anyone with a decent workshop should be able to do it themselves.
hard to say how much it would cost, prices vary, it all depends on how cheaply you can source the parts..