The gold color regulator is likely brass. Born and raised in CA, I feel obliged to remind you and others that in CA, EVERYTHNG causes SOMETHING....don't lose sleep over it. The brass is perfectly safe. If you'd feel better investing in the stainless, that's fine, too. We always use a regulator since some CGs have high, low, in-between or both water pressure, so it's just good insurance that you don't step into a situation where they have very high pressure. You'll find some CGs that have a built-in regulator on the spigot, so in that case just put yours away. Theirs will be fine.
Yes on the water heater and pump. Although we frequently forget to do it, getting into the practice of shutting off the water at the spigot if you're going to be gone for a while is a good practice. You just never know what could cause a leak and coming back to a flooded trailer can really ruin a nice trip.
The "pink stuff" is standard RV antifreeze and is harmless. DO NOT use regular auto antifreeze and don't let pets get near it....it's toxic. Do a search on this forum for winterizing and it will give you the details....not hard at all, just make sure you have pink color coming out all the faucets, toilet and the outside shower and then shut everything down. You're done for fall. When spring rolls around, just hook up to fresh water, turn on your faucets and let it run until there is no more pink color. Shut everything off. Add about 1/2 cup of regular household bleach and fill the freshwater tank. Either take your camper for a few mile ride or just let it sit for a couple of hours. Open up all the faucets again, hook up the fresh water hose and let it run until the bleach odor is gone. You're done. Everything is sanitized and you're good. BTW, when you open up and get all started in the spring, you need to put in a new water filter. There are various densities, so you have a choice. Doesn't really matter....our OEM was so dense we hardly had any water pressure. When we replaced it the next year we joked that it only stopped the gravel from coming through. Just read the labels or do another search here for recommendations.
We've all been newbies, so don't hesitate to ask questions. You can do a search and find more info than you ever knew you needed to know about. If you don't find what you need....ask away. Campgrounds are full of usta-be-newbies, too. If you run into a glitch, don't mind asking for some help....we've all been there.