Need Advice

[orca54]

I need some advice - My daughter's 91 LS 400 broke down over the weekend and was towed to a shop where the mechanic told her that the serpentine belt shredded because the tensioner siezed. They want $400 to repair. Does this sound right and is there anything else she should be aware of? She is a student and does not have experience with repairs and it is too far for me to go and take a look. Any and all advice would be appreciated before I call and inquire.

Thanks!