As I recall those things are fairly pricey. As for "need", I am a little mystified. I think those little Rugers were the first pistol I ever shot and I have been owning and occasionally field stripping them for a long, long time now. Back when cars had tailfins I thought everyone knew how to do it.
Some tricks: If the latch is really stiff, use a loop of thin electrical wire over the end to get it open. You can also take a fine file or stone and smooth and round that initial cam angle so it doesn't take quite so much to start it. To removed the (mainspring housing) msh pull straight down.If the barrel/reciever doesn't want to come off whack it with a piece soft wood (protect the rifling at the muzzle with something soft). Same for replacing it if it goes hard. If really, really tough, consider taking a proper piece of metal pipe about the same radius as the flared upper lips of the lower reciever (grip section) and tapping that to open the radius slightly. Do it carefully. The reverse (gentle squeezing together of those flared sides) will work to tighten up a loose fit.
When reassembling make sure the hammer strut is to the rear and will be engaged by the mainspring when you close it up. Easiest way is to insert the floppy pin all the way up to secure the barrel/reciever properly, then tilt the muzzle vertical as you close and latch the msh. If you feel pressure as it closes, you have it right. If not you missed it. Just swing it open and try again.
BTW, deliberately missing that so the strut does not go into the mainspring cup is a good way to render the pistol incapable of firing, yet readily made ready to fire with minimum fuss. Sort of a very early internal lock system...
+1 for the Volquartsen retrofit. I have put a couple of these in and they are worth every penny.