I installed "w_turbotax_1040_prm_2017.030.0100.exe" but now "w_turbotax_1040_prm_2017.050.0104.exe" is available. Should I install the later .exe file?

Just run a update.  Go up to menu item Online - Check for updates.
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There will be a lot of updates in the next 3 months ... keep your program set to auto update so you get them all timely.

 If you let the program automatically update, you don't have to re-download the installer. 

The downloadable installer is refreshed with each new update, so that if for some reason you need to re-download it, you will get the latest, or close to the latest version.