gas in the oil eh?
take the intake pipe off and have a look down the TB and see if the injector is leaking fuel all the time, the engine will flood, not start, and gas will eventually make its way past the rings and into the oil.
with that being said, the fuel driver in the ecu likes to go all the time as well, you may want to make sure your fuel pump is even running when your trying to start it....
BUT now that you took the head off to replace the head gasket, was the timing belt put back on right? was everything hooked back up?
its a big can of worms now to try and diagnose over the web. but we can try.....
-Lance