Looking to go from a V3 to V1 on a USP 40 Compact, where can I get the parts, and any idea what they cost?  Thanks!

How important to you  are the "SF" markings on the control lever?  If very, you need a V1/9 control lever, about $50, and a $15 V1 detent plate.  If the markings don't matter, all you need is the $15 detent plate.  Gun Parts Corp should have them and I am sure HK has them.  They are very easy to replace and there is no need to involve a smith.  If you can take off your slide, you can change the detent plate.  If you need directions look at any of the detailed strip posts here or on HKPRO and of course, only go as far as needed to replace the detent plate, which is the first thing you do after you take off the slide.  If the directions say take out the hammer spring first, skip that.  There is no need to remove the hammer spring for a detent swap.

Thanks for the lead and info BB.  Markings don't matter to me, so I'll opt for the $15 swap!