You are mixing up a lot of concepts there. The €10k is no longer relevant to you as you will not be living in the house - that only applies to the "rent-a-room" scheme, which doesn't apply once you move out.
You can claim 100% of your mortgage interest (plus your rental costs) against rental income, provided that the mortgage was used to purchase the rented property. I don't know of any ceiling to that. You will no longer be eligible for TRS and yes, I suppose you should tell revenue (don't know the process of who communicates what to whom, but that's the safest bet). You may also have to tell your mortgage provider as they may have given you your mortgage based on it being a PPR and you may have to pay a higher interest rate as it will become an investment property.
In order to claim your interest relief, you fill it in your form 12 tax return for 2008 (and 2009 when it comes to it).
Sprite