Does anyone know if I have to take off the complete unit with the cooling lines to replace the tensioner or can I just take off that little tensioner wheel. It appears the wheel is bolted on. But when I look it up at O'Reilly's they show the whole unit.

 

If you haven't replaced already, no need to take off the tensioner assembly, just remove the bolt on the pulley (left hand thread) and replace pulley.

 

The tensioner pulley is what I did. There is a dust cover on factory one that will not go on the store bought ( oriellies) I had to place a washer on the bolt to get it to freewheel when tight. In any case much better than replacing assembly.