In theory, again I state IN THEORY a fix could be possible, if your screen is losing lines and you don't mind possibly rendering it useless you could try to fix it, if you are going to have to replace it anyway it could be worth a try:
LCD screens often fail when the conductive rubber strip between the liquid crystal glass and the pcb of the display loses conductivity, this could be due to the ingress of dust/liquid/grime/smoke or the conductive grease sometimes used drying out. By dismantling the LCD assembly and cleaning the rubber strips it is often possible to restore normal operation.
I have never tried this on the MPC but I have had some success with other LCD screens, so if you want to attempt this you do so at your own risk.
Personally if I had 1 or 2 lines out I would not bother until the screen was unreadable, but if my screen was bad enough that I was going to buy a new one then I would definately try this.