Your printer will not be able to output this file correctly as long as the links are missing. What you are seeing on your pages is just a low-res preview of the images.
To fix this, you will have to find the original graphic files that were linked, and relink them to your document in the Links panel.
Image previews are stored in the file, so that's why you "see" the missing links. You need to relink for output.
What should I say. Yes you can print the document. Will it look nice? No. InDesign saves low res previews in the indd-file.
To fix the links just relink them. If you know where the original linked files are, go to your links palette and select a missing link. Hold the cursor over the entry to see in a quicktip with the original path.
Maybe this hint helps.
Thanks everyone - I appreciate the help!