Glow Plug Harness

[DirtBag]

This question might take the cake for stupid question of the day...but it's got me stumped.
I've noticed latelty that my truck, which usually get a VERY consistant 14.5 -15.5 mpg in the city is now getting only around 12.5-13.5. I've checked all of my filters, everything's ok.
I've also noticed some white smoke on startup latetly also, during cold weather. That made me think to check the glow plug relay and plugs.
The glow plug relay checked out fine, 11-12v on each of the big terminals.
Then i went to pull the harness going into the valve cover to check the resistance of the plugs......but i cant figure out how to get it unplugged.
I realize this makes me a moron....
Here is what i'm looking at....hopefully this picture works.

[DirtBag]

...and i hit the wrong button.
Anyway, so I pushed down the on top part which looks like it should move and let the plug slide apart, but I can't get it to budge.
It's also pretty cold here and so I"m sure it's a little more brittle than normal....and I really dont want to give it hell and snap it
I'd appreciate any advice.
Thanks!

[Turbo Rushmmm]

Right above the wires That little tab push down and pulle out on the plugg should come right out, you can put some peter in it, it should not break