Hello again!
In answer to your questions, bearing in mind I live in the UK -
I bought mine new direct from Silver Reed but they did come up on EBay now and again.
Yarn came from online yarn stores, EBay and thrift stores.
I had a yarn winder. You can not use yarn directly from a manufacturer’s ball or at least I could never manage to!
Intarsia carriage - I had 2 for my steel beds but at the time I was machine knitting there was not one for the 150.
Diana Sullivan videos are great!