Winterizing and stuff

[Curtis-79MH]

There are only two seasons here in Alaska: winter and construction! And winter is coming fast. I need to change antifreeze in my 79 motorhome before winter sets in. I have three options as far as I can tell: have a "quick lube" exchange the fluid ($90), do it the ol' fashioned way by draining the fluid using the petcock on the bottom of the radiator, or use a "flush and fill" kit available at auto parts stores. Anyone have greater success doing one over the other? I might add that the fluid in the system now is kind of rusty looking so I believe it needs to be flushed.
Any winterizing tips that you can toss my way would be great!!Thanks to all!!