Rails and modal jquery dialog form

I'm new to using jquery modal dialog boxes with rails and was wondering how I can :

1. show a jquery modal dialog box with 1 field (eg "title")
2. post this form to a rails controller (via ajax)
3. have the modal dialog form redisplay if field is not filled in (with normal red css in error field)

Any tutorials or examples welcome.

Using Rails 3 and jQuery. Thanks for your time.