The only two critical bearing sets are the centre diff and the input shaft bearings, they are both taper roller sets and need a bit of care when stripping the box. If you're going to replace the input gear, you'll need to disturb that shaft and bearings to get the old gear out and the new one in.
Better than me trying to talk you through it, get into RAVE and read up on it. Note that early TL230's had a crush spacer for the taper roller bearings in the input shaft, later D2 boxes have selectable spacers.
I've found most of the pictures, I'll post a few here so you can get an idea of what is inside the box.
First picture is the REAR output shaft and housing. Nothing too special there, that bearing is retained in place by a BIG circlip:
Next is the centre diff as it came out. I didn't disturb any of that:
Next is the intermediate shaft, note the O-ring on the bearing pin, you need to seal the other end where it goes through the case. The input gear is just out of shot on the right. Selectable spacer (D2) by the bearing pin, D1 has crushable spacer.
Next is the FRONT output shaft, bearing, circlip and the diff lock fork. Note that there is a selector ball and spring involved, plus those two flimsy circlips. That spring in shot is NOT the detent spring:
Next is the diff lock selector shaft showing where that large spring and two circlips sit:
Next is inside the FRONT output shaft housing looking at the output shaft end that would normally be inside the centre diff, and the centre diff front bearing track:
Next is the REAR output shaft and housing, assembled:
Another view of the same housing:
Picture of the stripped and cleaned housing:
Picture inside the housing, you can see the REAR centre diff bearing track top right:
Front output side of the centre diff without the housing, bearings are greased ready for assembly:
Front housing bolted to the main casing. The detent ball and spring etc it not fitted:
Front housing from the other side:
Almost finished!
There are two selectors and two sets of detent balls and springs that are hidden away by flush grub screws that can be difficult to find if the housing is dirty.
Hope the above helps. If I can find the originals (these are reduced) I may have more on the input gear.
Peter