I tried to put together a comprehensive wheel page for the G20 wheels and tires.
Try this...
http://www.g20.net/mod_wheels.html
In short unless it's a new, and I mean 2001 Sentra the wheels won't fit. The older sentras upto the new model change use a 4x100mm pattern. Then new Sentras use the same 4x114.3mm pattern that the G20 uses. Of course the wheels could have 8 holes with both bolt patterns on them, like the ones I just bought.