Moen faucet problems (stuck collar)

I have one of the single-handle Moen faucets in my kitchen that was installed by the house's previous owners, probably between 5-7 years ago. The handle started getting progressively harder to lift and turn, and I should've disassembled it earlier to figure out the problem, but I put it off until it was too late and the plastic pivot retainer snapped in half. So, I called Moen and ordered a new pivot retainer and cartridge. As soon as I popped the plastic lid on top of the handle off, I could see extensive mineral deposits - almost certainly what had clogged the cartridge, putting an increasing amount of stress on the pivot retainer every time the faucet was turned on or off until it finally snapped.
My problem now is that I can't get the collar directly underneath the handle assembly off to get at the large nut underneath it. It's stuck solid, and obviously there's no way to remove the broken pivot retainer or replace the clogged cartridge until the collar is removed.
For those of you who are familiar with these faucets, how much force should be required to remove the collar? The disassembly instructions don't go into any detail beyond "unscrew collar, being careful not to damage finish." I think that's probably a tad optimistic, as I don't see any way to get this thing off short of a larger adjustable wrench than I currently own and a lot of gouges in the collar finish. Is there anything inside the faucet that would be damaged if I squirted some Lime-Away in between the pivot retainer and the collar? I'm guessing that the same mineral deposits that clogged the cartridge have also frozen the collar in place.
Thanks in advance for any advice.
Dave
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Go to Moen.com. they have a tech support line. If you tell them your problem they will send you the parts free because all their faucets are lifetime warranted. You don't have to send in any invoices or the old parts, they are good to work with.
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wrote:

I missed the original post in this thread, but I think I know your problem. ROTATE the cartridge as you pull upward on it. That's the trick. You DID remove the snap ring on top, right?
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wrote:

To make pulling UP while rotating easier, drill a hole thru the white plastic piece you use to rotate and put the screw back in. Then pull up on the screw while you rotate using wrench/pliers on the plastic.
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They sent me an entire boxed "Riser" kitchen faucet kit, though I only needed a few parts for a repair. No questions asked.
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Chuck Reti
Detroit MI
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