There are dozens of resources on the internet to help you with Old English grammar. On this site, you will find Michael Drout's King Alfred's Grammar, a straightforward and clear electronic grammar with exercises. It not only explains Old English grammar, but also reviews Modern English grammar. Check out the OE grammar chart, too.

There is also an Old English grammar engine. You can do exercises in Old English and search the Anglo-Saxon Poetic Records. A new version is being developed which will interface with the corpus of Old English poetry. It will also (hopefully) parse sentences for you. I am also building a search engine for the Corpus of Old English which will be able to search for terms according to author, dialect, and date. These are both part of an ongoing interest of mine in computational linguistics. If you are interested in learning more about computational linguistics, I would be happy to speak with you about arranging an independent study.