lol
I have those kegs.
DO NOT REMOVE LID - UNDER PRESSURE ....
the warning continues under the relief valve.
vent it before trying to remove it (although I don't think if it's under pressure you can remove it).
When kegging, you'll need to add some pressure and guide it in place for a good seal. If you place the lid and lock it without adding pressure, it may not sit right and can leak. Once you have it in place, then purge the headspace air by a few series of venting and recharging. I do this about three times trying to visualize the volume if air that has been purged so that I am confident it's all virgin CO2.
The wide lid makes for easy cleaning. When I sanitize, at the end I out the lid on and hook up the CO2 and a party tap to flush the stem and out valve. I should hook that up to my faucet tower to flush the line after removing a keg - can't hurt sanitizing a keg AFTER a use right? I have to clean it anyway.
