leak
This spigot leaks from the place where the handle attaches. Would I be lucky enough to be able to just need to replace the handle? Or would I need to also replace that brass piece it's connected to? All I can tell you about the faucet itself is that it's an anti-siphon one.
I contacted Moen directly with this same question and they let me know that they recommended a model 1225 replacement cartridge instead (that's what I get for trusting the guy at the hardware store to look up the matching part for me). Technically either one will work but apparently the plastic 1225 offers a tighter fit than the brass (and more expensive) 1220.
Moen also recommended cleaning out the inside of the valve with an old toothbrush or bottle brush and then flushing thoroughly before installing the new cartridge.
I will update this once I know if the new cartridge resolves my leak.
Update: After the installation of the model 1225 cartridge, the faucet works without any leaks from the stem. With the addition of a new knob the whole fixture is working better than new.
The moral of the story here is, when in doubt, try to contact the vendor (and post your results!)
The next step secret to getting more of this faucet apart are the two slots cut across the cupped part. See the arrows in the following picture.
It looks to me as that the cupped part is threaded down inside the larger diameter part that sticks up from the hole in the sink. There is probably a special tool used to engage these slots to thread the part out. It may be possible to lay a piece of metal bar stock across these slots as a tool. If you do that make sure that it has nice square corners.
Best Answer
If you're lucky, with a frost proof fixture like this, you may be able to slightly tighten the nut that's holding in the packing or gasket behind the handle. You'll need to have two wrenches for this, one to hold the faucet in place, and a second to tighten the nut.
If this nut doesn't want to turn (don't force it, else you may damage it and then need to replace the entire faucet), then you'll need to replace the packing or gasket around the valve stem. It's a cheap repair, but requires the water is off to the fixture and that you are gentle to avoid damaging the soft metal.