Expect a LOT of gunk if that's an 03 and it's never been flushed = not good. The traditional green antifreeze used in these trucks is typically only good for 2-3yrs/35k or so, 8yrs is a LONG time. Expect to be flushing for quite some time, make sure your heater blower is open.
When you refill, after the radiator's full and you're attempting to get all the air out, make sure your heater blower is on high.
Also....change your thermostat while you're at it.
When you refill, after the radiator's full and you're attempting to get all the air out, make sure your heater blower is on high.
Also....change your thermostat while you're at it.