Just ordered my G20 ecu it should be here on wed of next week

Yes!!!!
it's a '95 btw
O

Cool, have fun. The first time you watch the needle climb into the red zone past 7100 rpms is insane!

Can I use a G20 ECU in my 98 Sentra SE?

Yes you can!!!!

O

Yes, although the G20 ECU works a little better in the 95-97 cars, the 98-99's you'll get a CEL and may have some idle issues.