The correct baud rate etc settings are 57600, 8, N, 1 (ie 57600 baud, 8 bit, no parity, 1 stop bit). You can verify this and see other details of specifications at www.fingertech.co.uk/gps_navman_3450.html
The other thing you may have forgotten that you need is to install the Navman driver - unless you have done this, you will get a "card not recognised" error when you slide on the GPS sleeve. This driver, version 3.1.6, can be downloaded from the Navman website.
I don't think you need to set the COM port number as a number, rather you select the Navman driver and it automatically knows which COM port is associated. This is COM 6 on my setup, but might vary between devices?
The other thing that some GPS software requires is to know the "type of GPS receiver" - this is "Other NMEA"