1. The swinging spindle is a tight press fit in the frame, add possible corrosion, removal is for the brave. Best done by a proper press. If you use a hammer and drift beware burring the ends.
When it is out the next issue is remove the bushes in the swinging arm, you may get them out with a drift or press or carefully saw a slot.
Then fit new bushes which will need to be line reamed to suit the new spindle.
Then press it all together not forgetting the spacer.
The Rupert Ratio Unit singles manuals very helpful.
2. Parts book useful. See photo from 1961 parts book.
3. Engine unit listed as 35 kg.
4 I use C and D Autos for many of the parts I buy. Very helpful and knowledgable if you phone them