Picture tubes and LCD's

Hey all,
Here's something I've wondered for awhile but am just now getting
around to asking.

Older CNC controls often have those little CRT screens that go bad,
or ghost, or burn in...

How hard would it be to replace on of those CRT's with an LCD and
what would be involved in the conversion?

While I'm here, let me ask the same question but subsitute the LCD
for a computer monitor of recent manufacture.


Thoughts?

Sean