Advise on Exhaust Pipe

[buzzlie]

Guys,My E34 met with an accident recently, backside dented. Now at the workshop under insurance claim. Need to change the exhaust too. The workshop just called saying they found a 2nd hand unit but want me to drop by to check the exhause pipe. Should I just look for any sign of karat? Any advise on what to look for before I say AOK for them to proceed and fix it? Once fix, cannot complaint already maa. Please, please ...