Moscovian might have an idea or two about the dark eldar, so it's not a completely lost cause...
As for Chaos, you don't have to do an overwhelming amout of conversions: many of the vehicles are the same, and the daemons come with the box set. The Warmaster range has some good figs for greater daemons. The odd war engines (decimators, deathwheels, deflilers, etc.) need to be converted. However, the decimators and titans require minimal work (if your group likes WYSIWYG - otherwise simple "counts-as" models work fine). Definitely do-able.
the current 'nids version is 9.2.1....somethingorother, under the Tyranid army subforum, I would think. Kind of complicated as a first army, IMHO, and it would require extensive ebay hunting/conversions.
EDIT: 'nid list pdf in Chroma's first post:
http://www.tacticalwargames.net/taccmd/viewtopic.php?f=21&t=15112