yes it will benifit it to cool it...
but odds are you already have a heatsink on it.....
it is a large chip, about 4cmx4cm and is located near the CPU, a similar sized chip will also be on the board, but lower down closer to teh bottom, that is your South bridge (and i have never seen a heatsink on that)
IF you are pushing your CPU into high FSB speeds then you will really want to cool your Northbridge better. If your FSB is still at 133 you are probly fine with the cooling as is.... But if you want to add more, it can not hurt....
If the Northbridge doesnt have a fan on it, simply adding a 40mm fan will do wonders to help cool it.