basically what you need to get is

the manual gearbox, unbolt everything and take the gearstick out then drop it out

the crossmember might be usefull for making one up later

the pedals, all you have to do here is undo the bar which they all mount to under the steering and slide all the pedals and little bushes off, then these will slide onto the one already on your car

oh and a clutch and pressure plate

now back to your car, you need to take the pedal in it out, undo all the bolts which hold the bellhousing to the motor, undo the starter motor, undo all the wires, take out the shifter, drain the oil out of the box via the drain plug then take out the tailshaft (undo bolts at back to diff)

then last of all undo the crossmember and slide the box out, fair bit of wrigling required to get it out, the box will be pretty heavy too

then there will be a big round thing where the gearbox was hanging off the flywheel, the torque converter, this needs to come off and be discarded, then you will be looking at the flywheel, there is a small hole in the centre, this is where the spigot bearing i was talking about has to go, check they give you the right one before you put it in as i got the wrong one once and had to drill it out (not good). The spigot bearing you just have to hit in with a hammer but use a block of wood or something inbetween it and the hammer to make sure it goes straight

now you are upto putting the clutch and pressure plate on, you need a torque wrench for this part, it is quite important to do the nuts to the right tension. When putting these on you need to get the clutch plate lined up exactly with the spiggot bearing or the gearbox wont go in, basically you put the pressure plate over the clutch to hold it in place and then do the bolts up finger tight so you can still move the clutch inside the pressure plate, then if you have a special tool you can use it to line the clutch up or alternatively you have to put the gearbox in allowing the clutch to move around so that it sits in the right position once the input shaft of the new gearbox is properly inserted into the spiggot bush. then carefully slide the gearbox back out so that the clutch plate doesnt move then with the gearbox out tighten the pressure plate onto the flywheel clamping the clutch plate in place, and put the gearbox back in again.

Now do up the bolts to hold the gearbox to the motor and try to figure out how your gonna make up a crossmember to hold the back of the box, i used a couple of bits of right angle steel and just ran it from the exiting holes which the auto box was mounted too to the bolt holes in the crossmember still bolted to the manual gearbox.

now get the pedals set up and hook up the clutch cable, put the new gearstick in, but the tailshaft back in, fill the box with oil, and then the other problem i forgot

the auto box uses six wires, two of these contol the starting of the car, i.e. car only starts in park or neutral, you have to join these wires together to complete the circuit, and also the other two wires together (cant even rember what they do now), the pairs will be like colours but not sure what color on a 120y, then the other two are the reverse lights these are the only two that need to be hooked up to the manual gearbox, there is a reverse switch on the side of the gearbox for this

and the other thing i forgot was the speedo cable but this is unchanged, unbolt from auto, bolt back onto manual

and yeah ya done, if your anything like me itll be 2 in the morning, raining and youll decide to go to maccas to celebrate, youll get an orange light to turn right across an intersection, decide hey i can change back to second and power through this, but youll change back to second and lock the back wheels spinning the car round and ####ting yourself, restart the car and drive on slowly hoping no copers saw what you just did

its good fun, i probably confused the crap out of you but if you want a better explanation (i didnt know how much detail to use where) ill be happy to re-explain

tell us what area you are in and someone may be able to help you out with a toque wrench or the tool to locate the clutch plate, you will also need to find out the required torque setting for tightening the pressure plate onto the flywheel on a 120y

i thought of another thing today, where the clutch cable goes through the firewall you need to get the special piece that holds it/guides it, and you will need to drill holes for the cable to go through and to mount this piece, it was obvious on the 1200 where it was supposed to be cause you could see where they tacked a piece on to cover the hole, its easier to redrill than attempt to take this off as the welds are generally stonger than the material around it.