Horrible car luck..what should I do next?

Here are the facts:

-I bought a 2003 Honda Civic hybrid used with 102,000 miles in October of 2010.

-In late June of this year, the car overheated. I had to replace the radiator and while repairing that, the mechanic discovered internal transmission failure.

-Two days later, for $3,500 at the Honda dealer, I got a new transmission.

-That was ten days ago. Now, the car was acting weird again on Wednesday so I had it towed to the dealer. They told me:

1. The head gasket had blown

2. As a result, water had entered the engine

3. The engine needs to be replaced.

At this point, I'm not even sure if it's worth it to repair the engine. I've considered trading in the car as is and seeing if the dealer will cut me any slack because they essentially sold me a lemon.

But moreover, has anyone ever heard of a transmission and an engine failing within 10 days of each other? I find it extremely hard to believe that Honda could not tell that there was a looming disaster with the gasket/engine when fixing the transmission.

Thanks.