No, don't worry! We will introduce Haskell gently along the way. If you would like to dig deeper into Haskell, we recommend that you read Learn You a Haskell for Great Good.
Please use our bugtracker. You could also fork the project and issue a pull request if you have a larger number of corrections.
Please just link to http://nlpwp.org/ to make sure that readers always get the latest and greatest version.