2001 Nav screen flicker???

[motetrault]

I had an aftermarket starter put in my car and when I went to get it my nav no longer worked--it just occasionally flickers. I took it to the nearest BMW dealer (9 hrs) and they told me the fix would be around $3000. I was just wondering if anyone had any less costly suggestions. I didn't know if it might work to just replace the computer system which is $900 but don't want to spend that if it doesn't work! Thanks