Auto subtitle downloader and syncer

I want to have a windows application (written in .NET) that automatically searches and download subtitles for any given video (movie) file. The application can use any kind of information (also metadata of the video file and characteristics found in the filename). Important is that the application should be able to check if the subtitle is in sync with the video file. So the application should take the following steps: 1. Check if there exists a subtitle for the given release of the video in a given language 2. If not download another version of the subtitle in the given language 3. If not one version found in the given language, download the subtitle in english 4. In all cases the application now has to check if the sub is in sync with the video 5. If not in sync try to sync the subtitle by changing fps or introducing offset 6. Clear the subtitle from any rubbish like the uploader name, any advertisements and so on (for this you can rely on a list of words/checks to determine if the text is an ad). I am a developer myself with quite some expertise but no time. For this I would like you to go in quite some technical detail in your proposal. I want to know which kind of technologies/tools/libraries you are going to use to accomplish this.