In LabVIEW version 6.1, just wire to a DAQ Channel name control as if it were a string control. For a simple test (I know, I just tried it), wire a DAQ Channel Control to a string indicator. Run the VI. The DAQ Channel Name selected in the control window will be displayed in the string indicator.
So, there is really no conversion necessary...the DAQ Channel Names behave like string controls in the block diagram.