Timing belt replacement costs

the other belt might be the serpentine belt.

First, why are you changing the t-belt? Is it cracked or loose (you can inspect it behind a cracked-open upper left front plastic cover)? Regardless, it's a three hour job plus under $300 for all parts, inc idler pulley and tensioner. (Note that the water pump is golden, so VERY rarely needs to be touched.) The outer serpentine is optional, as it's super-easy to replace in 10 minutes, and costs only $15. Get another estimate. I wrench who is practiced in replacing head gaskets on 2000-2009 OBs will replace the t-belt in half the time a generalist will, so the total quote will be considerably lower, Good luck.

Hmm, has it ever been changed ? Are you the original owner and how many miles are on your car? Replacement of the timing belt, tensioner, water pump and thermostat is like insurance to keep your car running in top shape. I know that a number of people will disagree with this, but, a single point of failure will cost you so much more than doing it at your convenience. It's your car and your choice.

Ignore Mark's "common sense kills the goose" advice, as it's not technically relevant.