Under Tools/Options, go to Library & Folders. Select Configure auto-import.
Add each folder that contains a type, like Series, Movies, Music.
When you add Series, select mode 'Include this folder and all child folders' and select video under 'Import these file types'. At Apply these tags, select Add and choose Media Subtype: TV Show.
Do the same for movies if you have them, but select Media Subtype Movies.
This ensures that when you run "Get Movie and TV Info'' it will query the proper database for info. But this only applies to newly imported files.
The best thing I think you can do now for the already imported files is in the tree view, go to Video, Files, in the Location Pane go to Series. Select all files in the details pane and choose Tag from the Action Window (bottom left). If the Media Subtype tag isn't shown, choose 'Show all tags' from the button left of tag header window (sub menu icon). Locate the Media Subtype tag and correct it to "TV Show". You can now select all, right click and choose 'Get Movie and TV Info'.
Correcting things in Media Center isn't very often a lot of work, its often only a matter of knowing how to do things the easy way. The advanced features can have a steep learning curve but once you get the hang of things it can be very powerful managing your media.