I believe they should be checked out, but I'm comfortable doing it myself. I'm not taking anything away from machine shops, and they can check things more precise than i can. But I'm comfortable with my inspection, and if needed, i can bring it to a machine shop to fix something I found. But if I'm going to pay a machine shop to pull them apart, inspect, etc., I'll buy the bare castings and have the machine shop do the valve job/assembly with the hardware I bought.