Actually, just use a spawn condition in the database. You may need to put the sentry and his werewolf form on a separate spawn group, or you might catch more then just the sentry with this, but basically, when it turns night, it will despawn the sentry and pop the werewolf.
What you should probably do is put the Werewolf and the Sentry both on completely separate groups and mess with the spawn conditions.
Tutorial on spawn_conditions here:
http://www.eqemulator.net/forums/sho...awn+conditions
I don't completely understand it, but it seems that the day, month, and year shouldn't make a lot of difference in the database, the big thing seems to be the hour and minute (the example shows 9 PM and 6 AM if I'm reading that right). I haven't messed with it, but let me know if you'd like me to try and set this up for you and I'll add it to my list this weekend.
In all reality, a quest event would probably be the easiest way to do this.
Now, the problem I see with your quests is that, unlike in Live, it forces a spawn right after something is killed rather then the mob actually respawning. The result? Easier farming. I don't know about you, but the one thing I can say about EQ farming was that it was suspenseful (and aggravating) because you never knew whether or not your named thing would spawn. If you do the spawning through those quest files with no timers, then you take away the suspense. Just by looking at it, it would seem more then possible for a group of maybe 4 people to kill Quillmane 10 or more times in a matter of minutes.
Just my thought on it. Maybe you should try messing around with the spawngroups. I wouldn't go this route to achieve what you're doing, though, unless you are going to add timers to the quests to give it a more live-ish feel.
Also, take out the debug statements when you try to release a quest like this if you would. It's distracting to the end user when they kill something and it says "Spawning Quillmane2." =P It's good for testing to ensure that it's working, but not necessary for your end users. =)