Cost to replace power supply

Does anyone have a ballpark figure on how much it would cost to have the power supply replaced in an iMac (early 2006, 20")?

I called my local Apple Store and they won't give me a price over the phone. I have to bring it to the store so they can look at it. I understand why they prefer to do it this way. I really do. However, I work 6 days a week and I don't want to spend a good chunk of my day off driving to and hanging around the Apple store (I have to wait even when I have an appointment) to get an estimate when I may or may not get it repaired (depending on cost). I'm just hoping to save myself a trip and time [possibly] wasted.

I'm positive it's the power supply. My father-in-law started the computer up the other day, heard a "pop" and the screen went blank. Now the computer won't even power up. I looked it up online and I would prefer not to do it myself as it appears to be quite involved.

Any help would be appreciated.

Thanks

Jon