dear if your mechanic is a good one ( which I suppose he would be) then let him decide on parts too. At one side we have the obsession of getting everything replaced by new one as we want system to be perfect, but on another that could result in waste of money and resources.
So if some of your parts in good shape, don't bother replacing them and I feel that might be what you mechanic suggesting you. Don't forget a good mechanic wont use a part that could ruin his entire job.
do share costs as well, and best of luck for the over hauling!
