You need to replace the LCD. I had mine replaced by Mikado in San Francisco, California. It's been a while, but I think it was like $150 for the job (plus probably another $60 for overnight shipping to and fro.), and they replaced the backlighting for free. Turn around time is nil--no more than an hour in my case. Here's the contact info that I used from k9crew:
the LCD in my '99 LS crapped out about four months ago. I sent it to Mikado in San Francisco and they did an excellent job of reparing it for $150. They install a new LCD that should last for many years. The turnaround was less than one day and I got my own unit back i.e. it's not an exchange deal. Here's the informatoin that you might need. Talk to Sammy ... he was very helpful and pleasant to deal with.
Mikado Technology Company
1435 Huntington Avenue, Suite C
South San Francisco
My before and after: