pulley tensioner

From what you describe it sounds like it's time for a belt change. Although a belt(s) can look fine they can be worn enough to cause squealing. After changing the belts if you are still getting a squeal then replace the belt tensioner. The worst part of doing the change is the tight space you'll have to work in. If you do it yourself the only cost you will have is for the parts. If a shop does the work I would think they would bill it out at about 1- 1 1/2 hours