Sears LXI 52" Projection TV help circa 1990

[Dan Schafer]

Hi All
My friend has a Sears LXI 52" projection TV model 626.54552190 that has been in routine service since apx. 1991. Focus & convergence are OK. Over the years however, it now appears foggy. A little like looking at the image through wax paper. I think it needs a good cleaning. Maybe something worse? Can anyone offer the proper cleaning steps or things to look for when inside the cabinet, for such a TV? I don't want to goof anything up and my experence is limited to 1970's & 80's CRT TV sets. Thanks in advance for any replies and suggestions or your 2 cents.
Danny in Cleveland