This might be a non-answer, but my honest advice for you is:
Don't do it this way.
As you are realizing, this method is really cumbersome and time consuming. It could be scripted, as @joojaa mentions, but custom scripts shouldn't be necessary for such a common task of matching screen colors to print colors.
CMYK colors are not absolute colors. They are a ...
Make a copy of your RGB colors put it in a folder called colors in document. Use only these colors. You can then drag the symbol swatches form one set over to anothers icon and it overwrites the swatch updating all globally assigned colors.
Now in illustrator you can just record an action overwriting one to another. But you could easily just script this ...
Printing onto metal is often done using silkscreen methods/equipment. And that would often mean using spot colors, and possibly having to supply multicolor artwork as separated, positive, transparent layers.
The advice to "always ask your printing contractor first" is especially important in this case, because of the unusual material. Ink and screening ...
I don't know if it's your case but...
In my case I can change it in:
Output > Image: Negative.
In these modes: Separations or In-RIP Separations selected.
Note that it's not available in Composite mode.
The subject is dealt with as "way finding" and of interest to architects and signage professionals. Secondarily, "readability" and "legibility" will be good subjects to review.
As a point of interest, red lettering on a blue background as you have in your example is another aspect of (poor) readability due to colour perception and contrast (which see) in ...
shows everything converted to RGB (as the PNG File is RGB). Looks like PNG will not get converted to CMYK, instead the whole file will be converted to RGB.
Two parts here.
A raster image inside PNG is no more PNG or JPG or whatever... It is a raster image inside a PDF.
The real problem here is that you are not using the correct PDF export setting.
A PDF ...
You have not mentioned anything about the color profile.
My usual example:
Take a marker and draw a line on a coated magazine paper, and on a newspaper. The ink value is the same, the color is not.
Leave your color as Pantone, the point of Pantone is that tries to be an "absolute color".
Define a set of color profiles, for example, Swop2, ...
As you are new to graphic design for now just set up the background as another color and let them print it.
So, do not worry about Ink, business are used to print things in full size on their printer, a photo, a poster, so it is part of the job.
Having a paper different from the background can be tricky.
First of all, you need to be sure that the paper ...
You have specified the expected print resolution as 300 ppi, which is what determines the quality of your printed image.
Consider that you can place the image on a portable storage device and provide it to a printing service with the above specification. Without seeing the image, you and the service will have the same expectations of resolution.
I've been creating a booklet file and adding the other files as pages to it before using the Print Booklet function. If you go to layout > pages > move pages, there's an option to move to another file, which duplicates it into that file. Make sure you move all pages.