Hi,
Screen flickering can be a sign the power inverter module for the fluorescent backlight is going bad. Also a screen backlight that is very old may fail to light reliably.
The inverter module is in the center between the hinges below the word, "MacBook," at the bottom of the screen. Inverters can be found from Internet suppliers for about $50. Do a Google search on the term, "MacBook LCD inverter." The fluorescent tubes are integral to the display, and not easily replaced, but you can replace the the whole display. The fluorescent tubes are designed to last about 6,000 - 10,000 hours. Depending on the display in your MacBook, the display can be replaced for around $200. I think I'd replace both the inverter and LCD together if I were going to replace the LCD panel. Something else you may want to order is bezel clips that hold the screen surrounding bezel; they are fairly easy to break.
Here are two how-to web sites:
http://www.screentekinc.com/lcd-removal-instructions_en,macbook.shtml
http://www.ifixit.com
--Bill