If the pads are OEM, and you drive normal, there is no way they should be worn down already. My OEM pads lasted 45K and my rotors lasted 70K.
Never heard of "Mountain". Brembo's are good, but for daily use make sure you just get the Brembo OEM replacement rotors, or "Brembo Blanks" (Avoid any drilled rotors for daily use). I replaced my OEM rotors with Brembo blanks, they have been great. You should be able to get the pads for $45-50 at a dealer, cheaper online, around $30. Brembo blanks should be about $50-80 online. DIY to save yourself some money