HELP water faucet cartridge replacement!

HELP , need help with water faucet cartridge reploacement:
This is a Price-Pfister tub water faucet cartridge. It came with inaccurate instructions and no one's at the 800 number, and I can't remove the old cartridge. Can someone help with this puzzle? I have links to photos, below, as well as a scan of the instructions.
This is a replacement cartridge from Price-Pfister, for this single-handle tub water knob. This is for one of those "self-contained" tub stalls that is built into new homes (this home is 5 years old). you pull the handle out to start the water and push it back into the wall to stop. With the handle pulled out, you twist it clockwise to make it colder, and counterclockwise to make it hot. Price-pfister sent me a replacement cartridge with (incomplete) instructions. The part appears to match the old one exactly from what I can see, and the instruction photo matches my tub handle, so I don't think they sent the wrong part. But I can't remove the old cartridge to replace it.
Here are some links to photos - I'll explain what the arrows are pointing to:
Figure 1, the single-handle tub control assembly with the handle and chrome flange removed, and the old cartridge still in there:
Figure 2, the instructions that came with it, which seem to leave out vital steps:
Figure 3, the cartridge itself (came lubed with petrol)
First, looking at Figure 2 , the instructions, I have removed the handle and wall flange and "sleeve", but now I need to remove the "collar". This is not shown in enough detail in the diagram of the instructions for me to tell exactly how to identify the collar.
Looking at figure 1, my actual tub handle assembly, I first tried to unscrew the brass colored collar with a pair of channel-lock pliars with layers of electrical tape over the grippers so they wouldn't scratch the threads. But the brass collar wouldn't budge. Then I saw, where the yellow arrow is pointing, a piece of black plastic is protruding through a channel in the brass collar, preventing it from being able to unscrew.
Looking at Figure 3, the actual replacement cartridge, the gray arrow points to the part that's keeping the brass collar from coming off.
Looking back at Figure 1 of the actual handle assembly, I then thought, maybe it's the silver colored piece (pointed to by red arrow) that's supposed to come off. If you look on the top part of that piece, you see a flat spot (and another one on the underside) where it looks like they made it so you can grab it with a plumbers wrench and unscrew it. So I tried unscrewing it, and the entire assembly and plumbing inside the wall starts to "flex" when I apply lots of pressure.
I stopped beause I dont want to break anything. As you already see in the same Figure 1, the black circular assembly behind the round cutout in the fiberglass stall is already been broken when they installed it; I think it was supposed to go all the way around the cutout in the stall, and now only a small piece is actually left holding it to the stall. This doesn't suprise me since the folks who built these houses did a real crap job, and they aren't even cheap houses. But thats probably a sore topic covered to death on this newsgroup.
Before someone suggests just call a plumber, the reason I'm doing this is I got laid off and cant afford it. Shouldnt have to call a plumber anyway; replacing a cartridge should be a piece of cake...
Can someone tell me if in fact the silver part in Figure 1 pointed to by the red arrow really is the part I should be unscrewing? If so, I'll go ahead and twist it hard with the big wrench but I dont want to rip apart the plumbing inside the walls.
Thanks in advance for help! - Good Music
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Got someone at the Delta help phone line later this afternoon.
Told them the problem, that I could not identify which of those two threaded circular pieces I was supposed to remove, and both were tight so I didn't want to break something.
Their response: "Rremove the circular one." I told them both were circular.
Their response: "It's the threaded one." I told them both were threaded. I asked what their email address was so I could send them a picture.
Their response: "Hold on, I have another call..." and put me on hold for 5 minutes, after which I hung up and took the big wrench to the silver part. This time it came right off with no effort... must have loosened it the first time.
So I got the new cartridge all in place and I'm re-screwing in the handle to the stem. Well, I keep turning the screw inside the handle, but it never does tighten. I take the handle off and try to screw the handle screw directly into the cartridge stem. It just slides in and out... the threaded hole in the stem is bigger than the one in the original cartridge stem! Looked closer at the packaging and it is labeled as "Proce-Pfister original parts"... We have 2 of these tubs in our house, so I tried the handle screw in the other cartridge they sent, same thing, hole too big... thats just wierd. Taking the second not-yet-installed cartridge to Home Depot with the original old cartridge and the screw to find a new handle fastener screw to fit the new cartridge... Hopefully the new screw won't be too big to fit through the faucet handle, or I'll have to drill out the acrylic faucet handle hole bigger...
man I thought this would be easy
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How about going over and buying a new one the same as what you have and see if it will come apart, at least you would know what direction to turn every thing.
I would say that the cartridge collar needs to un-screw in order to remove ( pull out the cartridge)

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