Q: is the fuel pressure regulator an engine job? or is nbd?

The fuel pressure regulator is part of the engine’s fuel supply system. The regulator is completely separate from any "mechanical" component of the engine. The purpose of this regulator is simply to maintain a specified pressure on the fuel supplied to the fuel injectors. If the upper manifold is already off, the added labor time to replace this part is typically trivial. The cost of the regulator is moderate ($60 to $100, depending on whether the part is OEM genuine from the dealer or aftermarket). Typically, the regulator will be diagnosed before it is condemned and that is the best practice so that you don’t spend money needlessly. However, during major work and or engine refurbishment on an older car parts like this will sometimes be changed out as a matter of course as cheap insurance against future breakdowns. In addition, if the part shows ANY visible sign of external leakage of gasoline it will be replaced automatically regardless of whether it works or not. Basically, for safety reasons, the acceptable amount of gasoline leakage on a vehicle is ZERO. Please let us know if you have further concerns or questions.