Read the Seamus Haney parellel-text Beowulf last year. I was only skimming the AS side of the page for the phrase here and there that can still be recognized as some kin to English.
What I came away with is a sense of amazement at how much the language changed from 1066 to Chaucer's day.
A good resource for Anglo-Saxon stuff is available on the website of Georgetown University... are you familiar with it? It has sounds and texts, including some interesting old spells for getting rid of warts and Wulfstan's Sermo Lupi ad Anglos (The Sermon of the Wolf to the English).
Old English is certainly very different from modern and as you say it had changed a lot by Chaucer's time: blame those Norman barbarians for some of that, I guess!