In answer to how long it will take?........ideally just a weekend.
Pedal box and fitting new clutch cable parts will be the hardest thing to judge on the time, not sure exactly what you'll need to do the stang.
Put your car on 4 axle stands, the more room underneath you have the easier it will be. Ideally a friend with a car hoist!!
Exhausts can be a pain depending on your setup. Mine was welded up as one piece from the engine to the tail pipe!.....so I had to hacksaw it out to fit the new box
Drain the trans/convertor oil. Drop the driveshaft (rear diff pinion bolts). Remove shifter and wires off trans / speedo / cooler tubes and starter motor. Put jack under trans and remove cross member and bellhousing bolts. Then steadily slide box back whilst lowering a little. Make sure you don't drop it on your head
2 people highly recommended. Then remove flex and sandwhich plates. Then it's a matter of fitting all the new gear and setting up the clutch.
Few tips (some from my mistakes
The flywheel has 6 bolt holes, but they are slightly offset and only goes on one way. Quite hard to torque them up....you can use some chain. Screw one link to where the clutch plate goes (Outer edge of flywheel) and the other end to the block. Stops the flywheel spinning when you crank up the bolts. Make sure you fit sandwhich plate first.
You'll need a clutch alignment tool. Don't fit the clutch disc backwards.
Remember to fit clutch fork & throwout bearing before fitting bellhousing.
When you bolt the bellhousing on, make sure you don't trap any engine wires on the top (you won't see from underneath, so make sure everything is held out the way.
Crank spigot bearing taps in by using the reverse side of a socket.
Mount your shifter after the box is in.
Don't fit an incorrect speedo cog. Make sure its for a T5 or TKO.
Don't forget to fill with oil.
Getting the input shaft to slip thru the clutch disc and into crank spigot bearing can take 10 seconds or all day!! Takes the magic jiggle. It's all about keeping the gearbox parallel to the engine. Once its almost in, you can use the 4 mounting bolts to the bellhousing to keep it square.
When the new driveshaft is in, you want about 20mm or 4/5" of the yoke showing out the back of the rear output shaft seal.
Murphy's law prevails everytime I take on a big job and the time always blows out. Never had a smooth operation yet
.....but don't let that put you off. The satisfaction later makes it worthwhile and you save some $$$. Practise makes perfect.