Sev

Hello all I'm new to the LOC having purchased a '98 Mk4 LS400 a couple of weeks ago. The issue I have is that the sat nav never displays 'GPS' and I have to manually plot my position every time or it doesn't work properly. I'm not sure if it's connected properly and I can't work out where the GPS signal is received so I can check the connection. Any help would be most welcome. Thank you. P.S. Also, is there a quick and easy way to replace the bulbs on the clock and temperature displays please?