I an thinking of an app for our college to make a library of answers of old question papers.
Students should be able to input old question papers and those who know the answers should be able to write the answers.
And then all the regular stuf such as sorting , filtering, searching, etc.
I have done this app using PHP and XML, but would like to do it all over again with the goodness of ajax, form validation, etc. using ModX.
All i can do with modX right now is convert a web design into modX template( with some template variables of no use

).
Can u tell me what are the things i should learn to make this db-backed app? I’m getting overwhelmed by widgets and API call examples in the documentation.