I went to Paris recently and took some pics of the Eiffel Tower at night with the Canon 40D/24-105mm. I didn't have a tripod but managed to prop the camera up with my backpack, water bottle, lens cap and a Paris tourist map. This is where the Live View feature is very handy for framing the shot since the camera was sitting next the ground and it would be very hard to look thru the viewfinder. Initially, I shot some pics in P mode, then aperture priority but none gave good results. After some trial-and-error shots, manual mode was the best and easiest. Manual focus, f10 for maximum sharpness, 10 sec exposure, lowest ISO to minimize noise (100), timer exposure to reduce camera shake. The light meter was not very useful in this case and I had to take several shots with different exposure times before getting the desired exposure. Try to find a dark spot with no nearby street lamps that can glare or fog your shots. This is easier said than done in real life since the areas near the Eiffel tower are well lit at night.
I also have the G9 but have not tried taking a night shot with it yet, but I am quite sure that it is capable. Be sure to try out your G9 during the day to familiarize yourself with the buttons so that you don't have to fumble around in the dark adjusting the various settings. I suspect that you will have to shoot in manual mode for best results. Good luck and have fun.
Chuong