Any sort of hobby soldering iron will do, get yourself one with removable tips and pickup a small (1mm) tip and you should be fine. Don't hold the heat on the legs too long as you can damage the chip although don't rush or you'll make a mess. If the legs are really small get a decent lamp and possibly a desk mounted magnifying glass too, they really help.

Get yourself a suitable flux pen too, makes soldering sooooo much easier.

Here's a PS2 mod-chip I fitted once which was all done with a cheapo iron and a 1mm tip.