Drain the antifreeze down and dispose of properly.
There could be different type freeze plugs, the ones I usually replace aren't much of a problem, if you can get at it. I usually take a chisel or something and hit the inside of freeze plug, toward the left or right side of plug. Don't hit the block. Hopefully that will turn the freeze plug, sideways in the hole, then you grab the edge of plug with pliers or vice-grips and work the plug out. I usually use a little sealer on outside edge of new freeze plug. Start the freeze plug evenly into the hole. Then I use a socket that just fits inside the freeze plug, tap on the socket to insert freeze plug. You can use the other freeze plugs as a guide to how far to insert.
I realize this an old post. In the future hope you don't have any vehicle issues, but, if you do, keep the site in mind. They are always working to improve the site and it's free.