Thermostat question 1.9d please help

[mathewst]

My thermostat is shot it seems.
Bought a new one (Mahle part), removed the old one.
New one doesn't have that bleed nipple as stated in manual.
Also the gasket is small and leaking all over the place now
The new gasket according to the mechanic goes around the thermostat egde (pulls on it cause it has a small grove in it).
If I put this on the new thermostat cannot slide it all the way it stays on the edge and when I put the cover cannot slide it all the way to screw it properly.
The thermostat I removed did not have this gaket at all, it had a large O-ring only with no groves and have no idea how it was mounted
This O-ring is larger than the hole where I put the thermostat it, thermostat slides a bit down.
According to vida the thermostat just slides in the housing and the (O-ring) goes on top of it then attach the hose and its housing.
But I cannot see anything that holds in place the old O-ring that I have (have no idea was this original or somebody just somehow stuck it there).

So here are my questions.
Do I throw away this groved new gasket and just somehow glue the old O ring till I mount the outer housing and hose?
If someone changed the thermostat on 1.9d engine please help