Core 2k is mostly AはBだ and related simple sentence structures. Spending a couple of hours with a textbook is enough to get the necessary grammar for it, minus a few exceptions.
You'll get the other words once you're a bit further down core2k. I'd focus on the vocab for now, as sentences were not really useful to me when I was that much of a beginner. What I did was focus solely on the vocab with just a bit of glancing over the sentences, and when i was done I made a sentence-only deck*. Made things much easier.

*core6k sentence only deck, I mean. I still have vocab-only decks.

I think its OK if at first you don't fully understand the grammar or all of the vocab words in the sentence.  I aim to learn just the vocab word that the card focuses on.  I'm about halfway through Core 2K and the further I progress, the less often this happens (in other words, the vocab you don't know on the early cards you end up learning in later cards).  The grammar is generally not too complicated - I'm about done with Tae Kim Essential Grammar and I generally understand the sentence structures.  So I would study grammar separately from this deck, since there isn't a lot of meaningful variety in 2K.

One thing I try and do, is read out loud the sentence on each card as I'm reviewing.  This is definitely a great skill to practice, as it improves your reading speed and fluency, and you become less tripped up by 'tongue twisters' and gain a better feel for the cadence and rhythm of the language.  (Make sure you have the native audio to go along with the cards so you can imitate that)