2002 C230K gas tank removal

[tcmo]

I noticed a strong raw gas smell after driving my car. It seemed stronger at the rear. Dealer said he could see small seepage from the top of the gas tank and said it would be 9 hrs labor to either replace the tank or find the leaking seal, hose,etc. I have the MB extended warranty and it covers "fuel tank" but does not mention anything about gaskets etc.
Does this labor cost sound correct? It's been single digit temps here-could something shrink enough due to temp to cause a small leak? Thanks.

[ILUVMILS]

The rear sub-frame needs to be removed to replace the fuel tank. The nine hour estimate sounds right.