If you have SV mags you won't need spacers. Although, there is a very slim chance that this could be an easy job. To fit a new barrel you will need a good gunsmith. Simply put this is not a job for the OK local gun smith.
It is likely that the slide, barrel, comp or more than one will need milled to fit. To go from 38 Super to 9MM you are also going to want to replace the extracted with an Aftech. Parts will run $300-4600. Also, Major 9 mm open guns are much harder to build, so it could require some serious tweaking as pert of the conversion process. You could end up with a bill for $300-$800 in labor. If you are willing to discard the 38 barrel and don't want to be able to switch back and forth, your price will be much lower, and the work will be finished much quicker. Finally expect the 2 week quote to finish the job to turn into 4-8 months. Remember most Gunsmiths, although they are nice guys with skills and good intentions are like black holes. The nearer your gun gets to one the more time slows down.