It's relatively simple...action block goes around/in the upper receiver/barrel assembly...put the receiver block with the upper in a good sized vice...it's made to fight the vise. The lower should NOT be mated with the upper...it should be sitting somewhere else on your bench!
Depending on the receiver block, it might have an insert for the inside of the upper receiver...mine didn't, but it seemed to work fine. I've heard some people say to leave the bolt carrier in if you don't have the insert.
Have at it with the receiver wrench...the delta ring can be a pain in the ass to work with; since I was gonna put a tube on mine, I cut it off with a dremel...the float tube has it's own barrel nut. I made two cuts 180 degrees apart, taking car NOT to mess up the barrel.
The barrel will be VERY tight, depending on how much torque went on it, and how many rounds have been through it, and whether they used anti sieze compound on the threads. I've even heard of folks having to stick the upper in a freezer for a while to break it loose.
Once you get the barrel off, just reverse the process using the tube's barrel nut...no need for a delta ring, spring or retainer clip.
A LOT of people here don't use a torque wrench to tighten the barrel nut...if you decide not to, then just hand tighten the nut, then crank it down 'til the next hole lines up straight for the gas tube. Install the tube, and tighten it with a good strap type wrench...I didn't have one, so I wrapped a towel around it and used a big set of channel locks, being very careful not to crush the tube.
Once that's tight, reinstall your front sight block/gas tube, and you're done. BTW, the sight pins may be real tight as well. Don't be afraid to give them a REAL good whack with a fair sized Ford wrench...sorry, I mean hammer hehehe. IF you're pins are tapered, make sure you bang them out the right way! It won't hurt to put some liquid wrench or Kroil on the pins, AND the barrel nut. Let 'em soak for a 1/2 hour or so before you start this project.
BTW, I made my Armalite upper into a paperweight trying to do this without the receiver block. Don't even THINK about it lol.
Make sure you understand what you're trying to do...it's not rocket science, but thinking about it a little before hand helps. Don't be afraid to ask more questions, either.
Good Luck!