Sorry Bill,but I dont have any old heads. There is Mercedes salvage dealer in Falmouth,Ky. that may have a good used head. In fact Mike may have a complete angine for your car.Call him at European Connections:1-800-395-8636.
I don't want to question your mechanic,but of all the Mercedes diesel engines I have rebuilt,I don't recall ever having to replace any of the valves. Just had them refaced and seats cut and lapped in.I don't remember about the guides, but they are not too expensive. I always replaced the seals. Maybe you need to check around for prices on the parts you need. I get most of my parts from the Atlanta area. Good luck,and keep us posted on how things are going.
Bill Lewallen Lex.Ky.