Belt Tensioner/Idler Wheel...

Hey all, my Idler Wheel (on, or next to, the belt tensioner) is squeaking to beat the band!!!! Can the idler wheel be EASILY changed out or do I have to buy a whole new belt tensioner assy? By easily, I mean simply: Can the thing be yanked off and put back on with nothing but the most basic of tools (like an open end wrench set)? I can't see the back side of the wheel, so I don't know if there's a bolt or nut back there or not. If it's a simple: "Remove bolt (or nut), Replace wheel, Replace bolt (or nut)" type of deal, I've got no problem doing it. Can someone tell me what I need to do?

Oh yeah, forgot to add a problem: I was doing 65 in 4th gear (LOADS of pedal left). When I shifted into 5th and gave 'er some gas, she started to vibrate pretty bad. Not large vibrations, but small, fast vibrations. When I dropped TO or below 65, the vibrations stopped. Is this typical of an '84 GLX?

'Preciate the info man! They DO sell idler wheels as a seperate piece, but after looking at the tensioner assembly I don't believe it would be easy to change out. I'm hoping that the idler wheel has gone bad and THAT is what's making it shake. So, the tires may need to be balanced for higher speeds you think? Sorry, I'm NOT a car mechanic. Give me a C-130 engine, and I can fix it... not so with a vehicle, don't know a dang thing about them!