Yes it will fit - and the CPU will also fit. It is an LGA 775 socket.
One suggestion: Before you remove the existing motherboard, take some digital photos of the inside connectors. The motherboard changeover is straight forward, but photos will come in handy when you have a question as to how the cables are routed.
Use an anti-static wrist strap before you start, and make sure that the computer is unplugged from any power source. When you connect the 24-pins connector, and the 4-pins CPU power connector, make sure that they are fully seated and that the latches engage.
Install the CPU and heatsink per established industry procedures. Use Arctic Silver 5 as the thermal compound.http://www.arcticsilver.com/pdf/appmeth/int/vl/intel_app_method_vertical_line_v1.1.pdf