Relationship between Icelandic and Old Norse
So, with the latter aim in mind, how useful am I likely to find studying Old Norse? Basically, is it likely to break my modern Icelandic, or will I find it helpful? I've heard all about how modern Icelanders can read the Sagas without much trouble etc etc, but I can't find much info from the perspective of people who aren't native Icelandic speakers to start with. I know about some of the differences, like the definite article, and modern Icelandic having extra vowels (hestr/hestur etc), and I'm pretty confident my brain can deal with switching between the two systems there. Ditto on minor vocab differences and pronunciation.
Can anyone help me out on the differences/similarities with studying the two?
x-posted with linguaphiles