^ what he said. You can normally find zerex g-05 in napa stores, and if you have time you might as well replace the thermostat too
Yep, doing the thermostat while the coolant is out is a good idea. I don't know about the thermostats you buy from Napa or Auto Zone or whatever, but the one I bought from the dealership (for the same $30 it would have cost at Auto Zone) while I was already there picking up the pink HOAT Mopar coolant, was an updated part that has a much thicker seal. I'm not sure if the leak I had from the thermostat housing was from running green coolant for a couple years (since that's what the wrong coolant is supposed to do, corrode certain parts) or just from the stock thermostat's seal being thin and eventually not sealing well enough, but the new one has a much thicker seal and replacing the thermostat fixed that leak. I imagine that's why they updated the part with a thicker seal, so I'd take the time to swap it real quick and probably prevent a future leak/drip from the thermostat housing.
By the way, you can drain your old coolant, remove the thermostat and them put the housing/hose back in place and do your system flush MUCH easier and faster with the thermostat out, since you won't have to wait for the thermostat to open up and allow the entire system to circulate. Also remember that approximately half the fluid is retained when you drain the radiator, half of the fluid is used in the heater core, hoses, etc. So if you flush the system several times with water, then when you finally fill the system with coolant, you DON'T dilute it as half the system will already be filled with water and will yield a 50/50 mixture when you fill the radiator with pure coolant. However, some methods for flushing/draining the system might allow you to drain ALL of the coolant, so in that case you would probably use the entire gallon of coolant and then fill the rest of the system with about another gallon of water (I think the entire system uses about 2 gallons, give or take).
I would recommend doing a final flush with the thermostat re-installed and then only drain from the actual radiator drain plug at the bottom of the radiator, which will only allow drainage of about a gallon of water (the contents of the radiator) and that way you can be sure to get that automatic 50/50 mixture. If you use the entire gallon of antifreeze and still need more, top the remainder off with water. Use distilled water for at least the last one or two flushes, preferably.