The "trick" I use for the spring assembly is this - I leave the barrel out initially, rather than put it in the slide first.
I take the spring assembly, put the front of the guide rod into it's special hole, but tilted up. I then take the barrel, slide it in under the spring, until it's hitting the back side of the spring assembly.
Then, using the extra leverage the barrel gives me, I push the whole thing into place.
