On the first question, my comment is that while the categories are easy to understand, the gig is to map sure which category the car you are looking at belongs to. In my case I thought that I am buying a well restored car, the description of work done was impressive. later on it turned out that many items were described in inaccurate or even false way. For ex. renovated boot floor appeared to be just a plastic layer painted in the correct dark gray. But while checked during the current renovation, I had to buy the entire floor sheets etc etc.
On the second topic: eBay is a great source of stuff, but a thorough check is a must.
So, as you may find elsewhere in this forum, it would be a wise move to go there with a mechanic and if the car is far away, you will easily find a local appraiser, including by asking on this forum.
Having said that, check some other posts about people considering buying and restoring Pagodas in the form of true rust buckets, so as they say Pagoda is an addictive disease, once you get it….