I would like to set up easyAIS to read GPS and other NMEA data in at 4800 baud and pass all of this data out with the AIS sentences on the NMEA out port at 38,400 baud.

Yes, all the NMEA and GPS input data with 4800 Baud are passed through and upconverted to 38400 Baud. (Together with the AIS Data)