i actually won a competition to go to this, so i was there on sat, and back on sun hence i didnt see a lot of amsterdam, will stay for about 4 days next time.
there WAS a 10k last yr, there were about 10 of us who won, i did the marathon along with another guy, 4 people did the half and another 4 did the 10k...
flights are really cheap over to amsterdam and you can even enter the race ON THE DAY! so you dont really need to go for a package, its easy enough to find the stadium and enter yourself