The parts book is a great help in showing you how it goes together, and what is missing. An original workshop manual is useful. These tractors are simple and robust and were designed for farmers to service and repair in the field.
It is also useful to look at a good C and take plenty of close up photos.
Some parts are still available from CaseIH, and some on this website under the Tractor Parts section, but your best source is someone like Don L or John S who post on this board.