If you delete a partnership on the device it deletes any data synced by that partnership - so if they are items created on the phone they SHOULD be safe - but if they were synced across deleting the partnership will delete the items.
What you should be able to do is create a second sync partnership as the device can support 2 PCs, or 1 Pc and 1 Exchange connection. Once you are satisfied that your data is sitting safely in outlook you can delete the partnerships and then re-sync again and everything should be fine.
Make sure you backup your outlook PST file though - its always better to be safe than sorry with these things