[kris]

The only thing you should be obligated to pay, is the original work you had done. The Timing belt, water pump, tensioner, coolant, and the labor. Everything else should be covered by the shop.

If they are a shady shop, they will pressure you to pay for it all. Hopefully you have the original quote, so you can verify there are no additional charges.

As for the OEM parts question, ask for verification. Dealer receipts, etc.