logic board/video problem

[Paul Bernhardt]

I need a rundown on all this because I think I've got it. My symptoms 
are screen suddenly going to half display, then completely blank. 
flickering on doing that occasionally. Reboot hanging, the spinner 
stopping, reboot failing to launch completely to desktop. In the middle 
of writing an email a "your Macintosh needs to restart, press and hold 
the on/off button until it shuts down, and press again to restart" 
error box (of unusual characteristic compared to standard dialog boxes, 
dark grey translucent). Right now it is working (I'm typing on it).

Is this the infamous video cable/logic board problem appearing? If so, 
if I get it repaired quickly does it increase the chances that only the 
cables need to be fixed and the  logic board itself will be spared? If 
I get it repaired quickly, does it increase my chances that I won't 
need to do another fix later (I read about repeated logic board 
replacements being needed.

Thanks for the input!

Paul