You're actually better off purchasing directly from N3V unless you already purchased from Steam because it's easier to manipulate your data. Anyway, this is how I'd do it.
To transfer content, you can do this a couple of ways.
1) Export your own personal routes, custom edited content, and sessions to CDPs. Then import those into TRS22 and download any dependencies. If you purchased any DLC, download it again and reinstall any third-party content such as that from Jointed Rail and Railroad Mods, or any other place you got it from.
2) Copy your TANE content-folder and create a new copy.
Copy the folder and rename the copy to something else such as TRS22-DATA.
Install TRS22.
Let it do its thing.
On the Launcher, you will need to click on Trainz Settings.
Click on the Install tab.
Click on the ...
In Explorer that opens up, browse for your "TRS22-DATA" folder you now have.
After the restart, TRS22 will run a DBR.
You'll have to update content, especially DLC packages, and may have some errors and warnings.
The advantage is everything will be there. The disadvantage is the extra work.