That looks promising! I think maybe a Loksound LS5 DCC L would plug into both ends of the larger green board once you remove the smaller DC "decoder bypass" board. The LS5 DCC's pins look like they'd plug into the 2 sockets like the ones on the standard LS5 DCC L adapter board seen here:
http://www.esu.eu/en/products/...-l-loksound-5-l-dcc/
That ought to get you track pickup, motor power (parallell wired), head and rear lights, ditchlights (if present) and speaker. That way you can run it without any soldering etc. right away, and maybe upgrade the speaker and better LED lighting later on.
But hopefully someone who's actually done this on this particular loco will chime in. The LS5DCC L ain't exactly cheap... 
But if you prefer to try the D408 you have on hand, we can talk you through what wires go where after you remove the green boards.
