Here is some useful info to keep in mind: Detailed news can always be found at the PSO-World homepage or at PSUPedia. This includes news from events. Also, a post in the forums will usually be made to announce/discuss a particular event (Protectors Spring Event).
There's a "Spring Event" currently in effect for the Xbox 360 servers. There are two missions for it (the second of which was just added the 15th). They both will be taken down on May 12th.
Protectors Epsilon (ε)
This one gives AMP by completing it. Check the link for more info about how much amp per difficulty/success rating.
Protectors Zeta (ζ)
This one does NOT give AMP for completing the mission.
Neither of these two event missions will give AEXP by default. As a reminder, though, if you have a character at maxed level (currently 180), any exp earned is considered AEXP.
Good luck and have fun!
ALSO:
PSUPedia and
PSUAmesani are two great resources to find info on missions such as enemy EXP, mission points, meseta, enemey levels, etcetera. I don't think PSUAmesani lists info for event missions, but PSUPedia does.