Vibrating Idle

I'm posting this on behalf of my mother. When her 2000 Alero is put in drive, and just sitting there with the brakes, the engine vibrates quite violently. I believe she said it's a 2.5L L4...

I looked at the tach, and it looks a little low on idle, atleast, I don't know what idle should be with this car.

http://img.photobucket.com/albums/v395/Evilweredragon/09-24-09_1439.jpg

Opinions? Also, when she puts it in P, sometimes it drops to only 200rpms nearly stalling before catching up again. On my car it's the complete opposite, goes UP in RPMs before dropping back to proper idle.

Sounds like the motor mounts need replaced. there are a total of 4 mounts, some of them are actually called tranny mounts (3 of them i think). Replace them all and it will be smooth as new. This has happened to me a couple times in the 10 years i have owned my 99 alero.