You must get the block drains out, it's ok if you pull the whole adaptor out of the block. You can then put it in a vise and use some liquid wrench to loosen the smaller plug for next year.
As for the passenger side, I guess it depends whether you are talking about a V drive or D drive. I use a short box end wrench, there is one spot where you can swing the wrench 1/8 turn or so.
I'd remove the thermostat too, there is some water behind it.
Follow the procedure, fog the cylinders, etc. You will be good to go for next year.