P.S. Also the retaining pin hole in the frame may not line up exactly with the slot in the barrel, and there is not much room for error. It is easy to bulge the chamber wall when driving in a misaligned pin. If the misalignment is fore and aft, the hole might have to be reamed for a slightly oversize pin, and that too is a delicate operation as the barrel is so thin.The problems are the radial alignment of the barrel and the tolerance of the barrel/frame fit. Experience and "feel" are very useful here, and there are special tools which simplify matters and prevent mistakes.
Take it to a gunsmith who has done it before.
Thanks, appreciate the advice on barrel removal. I was able to get my old barrel out with very little trouble. I've got everything ready to go back together as soon as my parts arrive. I had a .32 PPKs in stainless spotted in an area gunshop last year, but I was short of funds at the time(well actually most the time ) and could not snag it up in time. So this little conversion will work for a while until something else pops up. Since I'll have a PPKs in .32 I may just hunt one down in .380, there's a lot more of those floating around.No kidding! That is exactly what I did. You will have one more hurdle, when you try to install the ppk barrel the pin hole will not line up with the frame. It is close, but not close enough to drive the pin in and if you force it you will damage your barrel. All you need to do is install the ppk barrel and look thru the pin hole to see where you need to remove metal, then take the barrel back out and use a dremel to widen the pin slot in the barrel the direction that you need to go. Go slow, don't remove too much, there isn't that much room to play with.
I have since bought a real German ppk, so I just returned my PP to its original slide and barrel a couple weeks ago. For some reason I actually enjoyed shooting it as a ppk/s more than a pp, but I think that was because the sights were better on the newer ppk slides, and my pp is from 1968 and had the old style sights.