how do i re programme my laguna carmat sat nav?

hi there, i have been advised that i need to reprogramme my sat nav in my laguna initiale, 2003 the sat nav is the carmat range, does anyone know how to do this or do i have to go to the main dealer, he already quoted about £1600 to replace it, so not going down that road,strangly, the clock stops at the time when the engine is turned off, and has to be reset every trip, any connection