How do I add crop marks and bleed to already completed artwork?

I am a bit out of my comfort zone with this.

I have quite a few completed A4 pages in CorelDraw that need to go in for printing. They're all 210mm x 297mm but I need to add a 3mm bleed. And I also need crop marks (that's what the printers told me).

The finished product needs to be cut to A4 pages.

I need to know if the following steps I took are fine considering what the final product needs to be. So this is what I did with one of the A4 artworks as an example:

1. I double-clicked the rectangle tool and then used Ctrl-A to select all the content on the page and then I resized it slightly smaller than my 210mm x 297mm work area. This is just to make sure there was enough safe space and that none of the important stuff gets cut off. After resizing I deleted the newly-created rectangle. I didn't change the dimensions of my canvas at any point.

2. I went to Tools > Options > Page > Size and then I added a 3mm bleed. I also ticked 'Show Bleed Area' under Page.

3. I then extended any background fill that needed to be extended, just past the bleed line.

4. I published the page to PDF and in the PDF preset settings I ticked 'Bleed Limit' and set it to 3mm. And then I ticked 'Crop marks'.

I took a screen capture of the PDF and placed guidelines over the crop mark lines and nothing is cut off in my artwork apart from the background areas that needed to bleed off. Does that mean I was successful?

I'm kind of stressed out about this because it's for work and I think I overestimated my CorelDraw skills when I took on this project.