Whether or not to replace the tensioner itself, as opposed to just replacing the roller assembly is a tough question to answer. The tensioner itself seldom goes bad.... it doesn't have that much pressure behind it, and isn't going through any significant range of motion to wear it out. At 125 bucks, it's the second most expensive single part of the system (after the water pump). I'm torn as to this answer.... the roller bearings on the idler and tensioner pulleys are probably much more important, in terms of probable wear, than the tensioner itself. If it appears ok, and has plenty of "push" when you compress it as you go to change the belt, I suppose that you can go with just the rollers. I've never heard of a tensioner spontaneously undergoing a sudden catastrophic failure. Good luck.

Marty
'96 855T