I had similar problems with the LCDs. There is no sensible repair for the display-panels themselves. You can replace them but you need to ask yourself if it is worth the trouble.
I replaced my M505 with a M506, a much nicer unit with much improved user friendliness. For the plotter you could have a look on eBay to find a replacement. In Aruba you can use eZone (https://getezone.com/locations/aruba/) to order stuff in the USA at relative good rates. I used eZone extensively when residing in Curacao and Saint Martin with almost 100% good results.

The LCD are mainly affected by heat, humidity and UV, the tropics are a killer for these things. I had a Navnet 3D LCD looking horrible after years in the tropics. I replaced it with a used unit found on eBay looking much fresher and with a good display.

Regards,

Arno Luitjen
SV Luna
A54-121