This is what I had, a plastic bezel surrounding the TV, it came off woth screws
Sorry I do not have what the old TV looked like inside but I fastened the 3/4 ply to the metal side used by the old TV then ran the 3/4 ply between them and placed the mount. A little trim and that was it.
I can remove the very top piece by removing three screws, then just lift my new TV out, take just a few minutes.
Not too difficult however a person with a Journey needs to come along and give you specifics.
I assume you have a CRT built in. Normally these are surrounded by a facia or frame work to make it look finished. These facia and frame works are generally held on by screws or in some cases velcro or some of those push in keepers like found on cars etc. You need to find the method. For screws open cabinets on either side of the TV and look at the interior up near the facing. some times they are screwed in from the side. IF not then look for plugs in the facia, screws are sometime driven in a then plugged. The plugs need to be removed to expose the screw. Velcro or keepers simply require some pressure in the correct location to pop them loose. Look all around the outside of the TV cabinet for obvious spaces or telltale signs that it can be pulled apart.
My guess would be screws.
After you expose the TV you will see the method of mounting. I my case it was a metal casing side and bottom. There were bolts holding a shelf that held the TV. It was attached to the shelf by a brace. I was able to pull the bolts out and tip the TV down and remove it. Make sure you have help, these CRT models are very heavy.
Installing a new TV is just a matter of looking at what you have when you remoive yours and adapting to it. I used the metal frame work on the sides to anchor 3/4 ply as a base for a TV mount. Once that was doen I simply trimmed the TV inplace.
Some folks want articulating mounts or swing up designs so access to the rear of the TV can be available. Each person just adapts his own design. There are many thread on this topic so if you search you can find a lot of pictures and comments that are helpful.
Attachment 56339
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these may not help much but they some I took of the change.