Apart from filters and a Heater Bypass Valve, this was the first serious job I had to do on my Omega, and I have to say - first time I attempted it I gave up because I couldn't undo the b* bolt that Tunnie refers to. It comes out of the block at a slight downward angle which didn't help me.
Anyway, if you've got that far it's just wiggle-wiggle-wiggle back and forth on the transfer pipe bracket until it eventually loses its grip in the stat housing. You will have sore fingers/thumbs. If it's really really stuck you may want to spray some release agent in from the side and leave it a while.
Most difficult job I had after that was holding the new O-ring in place in the stat housing groove as I lowered it into the V.
Dave Elite was most encouraging and helpful on the OOF site for me. Just a small plug there...!

All I can say is 'persist'. If an old f#*t like me can do it, well...