The Porsche mechanics aren't going to tell you something to help you that does not involve you bringing the car in to them.
If you use the lead in the fuse box, I believe the car alarm will stop once you place the key in the ignition and turn the car on (not starting, just on). Otherwise just have a wrench/ratchet on hand and disconnect the negative lead your battery to shut the alarm up.
And buy a battery maintainer so this doesn't happen to you in the future.
