I need help with how to go about accomplishing this:

When the player is detected by a certain actor a script should fire which will trigger some events of my choice.

The problem is I do not know how to make a script that checks if that certain actor detects you.

Is it even possible?

Yes, you can http://www.creationkit.com/RegisterForSingleLOSGain_-_Formyour actor for the http://www.creationkit.com/OnGainLOS_-_Formevent.

Do I put this script on the actor?

Like Zartar pointed out, its simple if you know which actor that you want as your witness. Things get a lot more complicated if the witness needs to be just a random passer-by

Have a look at this thread I started a little while ago, B1gBadDaddy came up with a good solution and it works a treat:

http://www.gamesas.com/topic/1471502-how-do-i-make-a-scene-of-a-crime/

EDIT:

- Hypno