Later this afternoon I'm planning on replacing my standard handguards with a new 4 rail set.  Before I take on this task, am I correct in assuming all I have to do is compress the weld spring inside the delta ring, then slide the handguard off?

How easy is it for one person to do it without the handguard tool?

It can be done by yourself but it's much easier if someone can help hold back the delta ring.

Some of them are pretty tight, but the correct way it to brace the stock on something solid, and then pull straight down on the Delta Ring.  With the D-ring down, press/ pull out on the handguards.

Some are much tighter than others, but they all will loosen up a bit over time.

would be easier with two people but one could manage

I have CAR upper and the handguards are so hard to get on and off that one time I was putting them back on after stripping down the rifle to clean it and I was struggling to get them in place and when they finally went home the front of the rifle smacked me in the side of the head.  Now,  look at the front sight post.  It shall be respected!  That little bugger got me good.  It didn't help that when I wiped the blood away from my eye I had CLP all over my hands.  And people say the Phantom FH can be used for anti Zombie purpopses...