The G41 chipset is an economy chipset with very limited overclocking capabilities. With a CPU with a 333 MHz FSB freq, you will be lucky to achieve a 10% overclock.
This should be your first stop.
Core2 Overclocking Guidehttp://www.tomshardware.co.uk/forum/259899-11-core-overclocking-guide
Shadow's Gigabyte motherboard OC guide:http://www.tomshardware.co.uk/forum/page-245679_11_0.html
It's for an EP35-DS3L but all the Gigabyte Core2 BIOS's are similar.
For a G41 motherboard, set your memory multiplier to its lowest value, probably 2.0 or maybe 2.4. Push your FSB freq as far as you can. That will be around 350 - 360 MHz.
With the stock heatsink, you will probably reach 70 C before you reach Intel's max recommended vcore of 1.45 volts.