The main documentary which I watched as a source for this episode is this Discovery Channel documentary which aired roughly around the time of the last legal dive to the wreck per the YouTube description. The documentary gives a fairly thorough look at the disaster and provides a great deal of visual information if that’s something you like to have (as I do).
The Coast Guard report on the sinking can be found here, and the National Transportation Safety Board accident report is found here. Both documents are fantastic sources of detailed information regarding the sinking.
The Mighty Fitz by Michael Schumacher is an excellent book on the disaster which covers everything from the building of the ship itself and the precise details leading up to the disaster to the history of shipwrecks on the Great Lakes.