Makro Text ersetzen
Unfortunately, LISP doesn't work with LT. A macro or script cannot work with a command dialogue, some commands offer an alternative text-based sequence but 'find/replace' is not one of those, which makes the find command a one by one process in LT, unless you have the exact same text multiple times, then you could use qselect to select all matching items and then make the change in the properties palette, this won't work for matching one word in different text items. Though that would find all sentences with that one word and select them allowing you to isolate those objects which would make them easier to find.
Accepted solution
There is just one other way if you are feeling adventurous, save a COPY of your drawing as dxf (which is just a text file) use Windows explorer and open the file with Notepad which will let you use find/replace on the file, just be very careful with this method because if any of the words are used by the 'System' then you could destroy the file or have unexpected consequences. So definitely only try this on a copy and don't try it if you think any word might be a program-specific word.
For example, I would be happy to replace the word 'elephant' but would think very very carefully before replacing the word 'mouse'.