My 2001 BWM X5 had the battery jumped and now the Nav screen just blinks every few seconds and never comes on completly. The radio also now shuts off after about 30 seconds of playing. I am not sure if the screen is now bad or the nav unit. BWM dealer just wanted to replace the screen and nav computer for 3,800. What should I try before replacing these components?

FYI...I have the 4:3 screen, not the 16:9.