re: MB, tell me the best and most essential classical music I need to listen to

See if you can find an old booklet called The Basic Repertoire. It was written by Martin Bookspan who was an writer for Stereo Review magazine. You might be able to find one on eBay. It contains not only the pieces of music but the best recordings of them to get. He used to update it every now and then so there are probably several different ones out there.

You might also look for the Penguin Guide to Classical Music. It's a similar sort of thing but also gives reviews of conductors and orchestras.