Best way to disconnect the heater?

[05crewcab]

My heater controls are shot, the A/C has long since been removed...in fact, the only things that work are the HEAT(on all the time, but no fan) and the adjuster lever to change it from the A/C vents to the floor vents.

So my question is... what is the best way to turn off the heat? Should I contort to get under the dash and manually change the dampers from heater to vent(and where are they?), or should I just cut off the coolant lines to the heater core?

If I go route number two, how do I drain the heater core completely? And, is this bad for the cooling system in any way?

Thanks