Why don’t you just install it to a different dir, then start it when you’ve stopped the old version. It may work to just replace the g3tcp_server_32 file, but I’m guessing this is not a Genesys supported upgrade path!
This solution should work, but is not recommended since not the same major release. You have to update the TLibrary. If you do decide to do things this way, do not forget to update also the *.lms file. If you run into problems and need to look at the logs if you don’t have the right version of the *.lms you might not have all the messages in the log file.