Apps CalDAV/CardDAV application, how to proceed?

[pengintamago]

I have a CardDAV/CalDAV server that I have worked on. My next step is to create an Android application that will sync with it (cannot use existing CalDAV/CardDAV clients).

I have no Android dev experience, so I want to know what I can/can't do so I know how to approach this.

1. I am under the impression that Android has its own proprietary format that it stores calendar/contact data. The CardDAV/CalDAV server uses ical/vcard respectively. So would my syncing client have to convert data back and forth between the formats in order to store on Android and store on my Server?
2. I want users to be able to manually sync/change settings from the calendar/contact applications themselves. Does this mean I would have to roll my own or could I integrate these features into the default Android calendar/contact apps?

Thank you for any insight!