Respectfully, if it was done right then it should work for years without issue. We have a lot of experts on K7000 here and if you stay curious and friendly, I bet a local member might even drop by to check your tubes, etc.
This is a preservation forum, asking about how to convert to LCD is like going into a Mustang forum and asking about Chevy 350 swaps.
But then again, it's your property so you do you.
As others have mentioned the Unico model should drop in without a converter. The mounting is the issue as you will have to fabricate something to make it work.
As far as that will last the long term? I can tell you the Unico monitor is a new company with a first-generation product. Who knows how long it will last or if there will be more when it dies. I can tell you that there's thousands of K7000s in the wild that have been running full time for decades.