If its the original housing and has never been removed, it may take some patience to get out, but a pair of channel locks will be helpful...just keep wiggling it around from side to side until you can pull it out. It will not come out by hand.
There is 1 bolt holding the U-clamp that presses the housing into the block with an O-ring on it, you'll most likely need a new O-ring if one didn't come with the thermostat.
Remove your intake MAF pipe/tube and anything else in the way to give you more room as needed. May need to lightly tap on it from various angles to get it "broke" loose. You may want to consider getting a billet aluminum replacement.