2004 Nissan Pathfinder thermostat replacement

My 04 bucket o bolts has been running hot. Going from normal range to hot and back down with radiator dumps. Figured this to be a stuck stat. Boiled over today. Nursed it home with cap under no pressure and heater on. Removed stat running to lower radiator hose. Local outfit doesn't carry this. Have to go nissan. Local outfit says there is an upper and lower therm? Upper hose seems to run straight into tubing running to rear of engine. Cannot see back there well, cant believe that a stat could reside there. Does this thing have 2 stats? Also have trouble code in system now, p1217 happened during overheat. Can you decipher? Thanks Rick