altima drive shaft installation

Hi,

I need your help on inserting drive shaft into tranaaxle
for 97 Nissan Altima GXE Automatic (driver side). The
old shaft is already out of the car.

1: Nissan manual refers to a tool (J34297) to set along the
inner circumference of the trans seal and then insert
drive axle. Is this tool necessary to have.

2: Per Service manual, be sure to align serrations of the
axle shaft and then withdraw the tool. Question is that
serration need to align to what. I can not see inside
of the tranny through seal hole.

3: Serrations on the half shaft are shrap, how to protect the
seal from serrations cutting into. Trying to avoid fluid
leak.

4: How to make sure that circular clip or snap ring at
end of the shaft is properly meshed with side gear.
What if clip is not seated or meshed, does this clip needs
to be aligned when shaft is inserted.

5: Is trany has to be in park or neutral when shaft is
inserted.