You can see the serpentine belt, but to see the timing belt, you have to remove the plastic timing belt cover. I have no idea about when the serpentine belt should be changed, but the timing belt should be changed, I believe, every 70,000 miles. I just fininshed (like, 2 hours ago) replacing my timing belt, idler roller, tensioner roller, and crankshaft (oil pump) seal. I gave the car a good test drive, and all is well.

It is VERY easy to change the serpentine belt. The only hard part is removing the tension without a 3/4 inch "thing" to move tensioner, but I improvised, and all is well. I think I could change the serpentine belt in about 10-15 minutes now.

I hope this helps,
Stuart