I have a question regarding conversion kits. I currently have an XDm 3.8 .40 and am interested in getting a conversion kit to go from .40 to 9mm. Would I just need to buy a 9mm barrel and mag to fit the 3.8? I love the work that I've done with my .40 but not really wanting to buy a whole new piston in 9mm. also would I have to buy new guide rod springs or is that only if I want to go larger like to a .45? any help is appreciated thanks very much in advance.