Very thorough comments, IT.

You can also look at LH First out of BOS.

If you are not hell-bent on absolutely getting First, opt for J (Business). Many more options, and many airlines have a lie-flat seat which make for a decent night's rest on the overnight TATL (transatlantic) flight. J is certainly a nice step up from Y (economy) in terms of space, comfort and service (and this is subject to a broad range of opinions and experience ).

In any case, and any cabin, availability will also be the question.