If your update stream is set to TRS22 it should be offered each time you start TRS22 SP2. Beware that lots of users had issues with the TRS22 SP3 patch. I opted to stay at build 122418 until a better patch is available.
I'm fine with that because it also doesn't have sparkling trees. Now the beta of Trainz Plus has apparently fixed that bug, I'm content to wait for a future version of TRS22 to include it too.
If your update stream is set to TRS22 it should be offered each time you start TRS22 SP2. Beware that lots of users had issues with the TRS22 SP3 patch. I opted to stay at build 122418 until a better patch is available.
Nothing wrong with doing a clean install. You can even keep your old install if you wish. I have multiple installs. Just don't access your local folder from the old install while using it with the new install. That can trash the database. I would make a backup of your local data folder on an external drive just in case.