http://www.toyotasurf.asn.au/techsite/powersteering.htm
here is a pretty detailed how to guide with lots of pics.
it just says rebuild in reverse which doesnt help much, but ehre is a few tips.
1st the retaining bolt was not on my box (i thinik its only on the ifs box)
2nd make sure the center housing is in straight/level with the teeth so it doesnt twist out of place
3rd when trying to twist the imput shaft back in with all those bearings, coat the bit the shaft slides into with grease to hold the bearings in place then push them into the grease one at a time until they are all in, then carefully twist the shaft back into place. - its easy with the grease.
4th if you do step 10, make sure its done up spuer tight again when done. i made a tool to fit into the holes. if the input shaft can move in or out at all then you will have lots of play in your steering wheel, like 1/2mm ends up being 4-5cm on the steering wheel.
sometimes the inputshaft seal cant seal due to pitting and wear on the shaft, this can be chromed and ground but $$$ and lots of them. i got around this by fitting 2 seals in series there was enough space in the box to fit 2 and this meant the second seal contacted on fresh shaft which hadnt been rusted or worn by grit in the old seal.
its a pretty easy job just be super carefull not to loss bearings etc.