Most concert photographers use something in the realm of the 70-200 2.8 lenses. Obviously Nikon and Canon both have them and they both have versions with Image Stabilization. I don't know if they make something of that sort for the Panasonic...
Don't know anything about your camera, but best settings -if you have good manual control over your camera- are:
1. a high iso (800 to 1200) because there is usually very little light
2. largest aperture (so smallest f number, f/2.8 or lower if possible) to let in max amt of light
3. autofocus. you don't have time to manually adjust focus, things move around way too fast on stage
4. shutter time around 1/100 of a second, preferably faster (same reason as above)
5. shoot in raw. this will give you most abailities to fix things afterwards