I drive a 2004 f150 with the 5.4 liter V8 i recently started showing the trouble code p0128 which is that the engine is not warming up in a specified time i believe that my thermostat is stuck and needs to be replaced i was wondering if anyone had any advice on the difficulty or the procedure to do this

 

I'm a little confused by that CEL - OBDll code.
Official description according to OBDll is:
P0128 -Generic- Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)


According to the description, it sounds like to me that your coolant is never reaching temp for the thermostat to open, but on the other hand, you are probably reaching temp and a signal must go to the PCM to let it know that the thermostat opened.
Anyway, I have changed alot of thermostat's in alot of different vehicles and never had a problem. Some are more of a pain than other's but it is really a straight forward job and usually less than $10.00 for the new thermostat and gasket. I had mine done with a coolant flush in less than 2 hours and that was with everything cleaned up afterward. Hopefully, someone with your same year truck will jump in and give you some tips, if there are any. On my 1998, removed 2 bolts, pulled out the thermostat, scrapped off the old gasket, cleaned the mating surfaces with scotchbrite, installed the new thermostat (properly, is spring down torwards block), reassembled, tightened bolts. Good to go.

 

My grandfathers 05 has the same code, and he mentioned about the time the light came on, the motor temp gauge only would climb half as high as it would normally. Anyone have any other tidbits to offer? I am also assuming it's the thermostat malfunctioning