I'm not aware specifically of anyone who has mentioned moving over from the plugin to ClassiPress, but in this instance you would likely need some knowledge of mysql admin in order to ensure that ads are migrated over to the correct place, particularly if the plugin creates the ads as "Posts", as ClassiPress uses custom post types. So if you're comfortable with mysql admin and creating a custom script to move required data in bulk (assuming you have a lot of ads), then it can be done.
ClassiPress does not include an email filter as described, so that would require customization of the default theme on your part if you were looking to add this functionality.
You can create Membership packs in ClassiPress as seen here in the
admin dashboard, however this is for actual ad posting. Thanks.