The fog lamp on the driver side of my 03 Legacy SLE just went out. Is this an easily replaced part and if I replace 1, should I just do both? In the manual, it says that it should be done by the dealer - how true is this? Also, how expensive are they?

You should be able to replace them yourself.

I'm not sure from your post if you realize that only the bulb gets replaced not the entire light. Either one is a driveway job. Some of the soob fog lights are outrageously expensive. I've got a 96 impreza missing both lights. OEM are $300 a copy. The bulb is probably $7.00.

That's great news - how do you get to the bulb on a 2003 Legacy.