2000 Accord 2.3L coupe

Saw a leak coming from the thermostat housing, the part where it connects to the metal tube to the water pump. It is the Thermostat HOUSING, not the case that covers the thermostat. I removed the 2 bolts holding it. It seems like the only other thing holding the thing is the O ring. It is very tight and it is also a 24 years old car, I don't want to break any unnecessary parts. Do I just force it out or is there something else holding it? If I have to force it out, any tricks to loosing it?