few questions about assassins

[Slig]

I was wondering if someone could help me. I know I can hide an assassin within a unit but I was curious about a few things.

1) for point cost, do i pay for the assassin and the unit he is pretending to be, or just the assassin and the other unit is a marker?
2) can i place him in my back line and then unhide him and charge him forward when i feel like it?
3) if he happens to get attacked by missile arrows, and is hit, is his cover blown?
4)can you redisguise him after his cover has been blown?

thanks

[==Me==]

Assassins are characters that join your units, you just don't announce to your opponent which unit he is deployed in.

[Daemon663]

you pay for assassins as if they were independant characters, then hide it in any unit u wish at the start of the battle ( given its an infantry unit ). you can unhide and charge yes, he can be shown at the beginning of the turn or the beginning of CC phase. if he is hidden and the unit is below 5 models, he cannot be hit and is still hidden, if all models die, he is automatically slain as well without having a chance of being revelaed

ps. why should u reveal and unhide him again ? but anyway rules dont allow that.