2002 Chevy Silverado 2002 duramax diesel

Im having a issue with my 02 duramax. I had a injector issue, it was filling the crank case with diesel fuel, I got that fixed, got my truck back and now it smokes like crazy. The smoke is a blue-white color and the shop still insists that its the injectors. But now their telling me because of the injectors that the smoke is coming from ignition timing. Im no ASE certified mechanic but if there is a bluish-white smoke it usually means it burning oil right. Iv done some research and what iv found other than the obvious, rings or valves how do i check to see if theres a turbo or head gasket problem. Iv already spent over $3000 on this thing and Im done with going to the shop and gettin bent over everytime i walk through the door. The truck runs strong but smokes like hell and now Im faced with this new smoge inspection. Any addvise will be greatly appreciated. thanks Tim