I have taken DL 31 twice since operations migrated to SVO2-D (and around 20 times from SVO2-F). As Naranjero suggests, there's nothing remotely complicated about it. There is now (following the attack at DME) general pre-screening of all bags at the entrance to the terminal, but there is no longer pre-screening right before check-in or hand searches as was the case at SVO2-F. DL's check-in (dedicated to DL & not shared with other airlines) is ordinarily around counter 41, immediately to the left of the entrance to customs/passport/security, but in any event you can check the screen (online check-in is not possible). There is an SP counter with little to no waiting.

Once you have your BP you walk through the green customs lane (presumably) to passport control, then to security, and then you have a pick of two basically identical lounges. Both times I have gone from check-in to the lounge in 5-10 minutes. I would feel fine getting there 90 minutes before departure, but if you are coming by car I would plan to arrive at least two hours early due to traffic on Leningradsky Prospekt (less of an issue on the weekend). Personally I prefer taking the Aeroexpress train due to the certainty of arrival time.

Anyway, relax, you'll be fine. I'd say the whole process for DL 31 is easier than for DL 30 or DL 46....