it depends on the reason it was removed in the first place.. if it was because some cap backwards wearing chav couldnt get his car low enough because the arb was rubbing the drive shaft and he was too thick to investigate a solution then fitting a new one shouldnt be too difficult.
if it was removed because the tack nuts mounting it to the subframe had sheared then it may be a little more of a task, though, i doubt very much it was removed for this reason and was removed due to the first one i mentioned.
