OK, so I had a problem with overheating a week ago, and it turned out
the head gasket was gone. After having my mechanic clean out the
engine, adjust the timing, and replace the head gasket, everything was
fine and I made a 700km trip with no problems at all. One thing I did
notice was that my fuel consumption was up significantly (18mpg down
from 26mpg).

I was driving around today (regular speed, and regular outside
temperature) and all of a sudden smelled this rotten fish kind of
smell. Right after smelling this my engine temperature went way up to
the red, and stayed at the red for a few minutes before going through
the roof.

Opening up the engine and checking it, there was some sort of leak or
explosion of oily water all over the engine compartment. The oil and
coolant levels are ok, and the radiator fan comes on, but the radiator
itself is cool. On the way back home, the car stalled going up a big
hill (from about 2000rpm) for a second and then started again. After
parking the car, the engine would emit lots of white smoke when trying
to start, and wouldn't catch unless I added gas or roll started it. Any
ideas what the problem is and how much it might cost to fix? Could it
be something with the water pump?

Thanks!
Theo