[Radek]

No special requirements. Even a mage can become an assassin. Only one thing, assassins seem to be best when they are equipped with daggers. If you have a dagger specialist then think about promoting him to an assassin. But an assassin equipped with swords is also very good.
As far as the Writ is considered, Bungleau may be right. I posted the message because I wanted to prevent others from getting frustrated by not gaining the "job". Naturally, if you find the Writ, you also find Grundel and have completed the first Santhril quest "on fly". Most probably, if you let the Writ be and return to Scanthril after seeing Grundel, the quest would be completed, too. But - I always took the Writ when I saw it [img]smile.gif[/img] Perhaps, it's time we made an errata: replace "have the Writ" with "have seen Grundel at the Writ" in my post.
Anyway, Scanthril will not take away your Writ. You will not offer it to him. Because you have seen Grundel, try to ask "job" immediately. that's all.