You need to ask your friend to send you the linked images and the fonts he/she is using. It's normal the files are missing if they're not embedded and if they were not provided in a separate folder. Since it's your friend,it shouldn't be a big deal.
If it's not really your "friend"... You can try these 2 things (doesn't always work):
A) Change the extension of your .ai to .pdf, and open the file in Acrobat Pro. Then use the "edit text/image" tool, right click on each images, and select "edit with Photoshop". Then resave them and relink them in the .ai file. Doesn't always work but maybe you'll see the image files.
B) Do the same as above but instead of right clicking on every images, export that PDF into XML (you'll find this by using "save as", and then selecting XML). Use the max image quality; You should select the images setting to export them in tiff at 300ppi... unless you know the images are not at 300ppi (e.g. your project is for web.) The images will be in a "images" folder with your XML file. Open your .ai and relink these images. You'll probably need to resave them properly in CMYK mode in Photoshop first. If there was some clipping masks on these images, they'll be cropped already.
There's no magical and easy solution to this. The best is to have the original linked files as you can see.
Once you got the images, you can relink them in the "links" window or when opening your Illustrator file. You simply need to point to Illustrator where it can find these images.
You can embed them later once you're done with your editing; if you plan to export your file as PDF as a print-ready then you don't need to worry about embedding the images.
If you need to edit the image files (e.g. color), you'll need to open these linked images in Photoshop and then update your links; Illustrator should prompt you anyway to it if the linked images were changed.
The fonts will need to be installed in your system or you'll need to get a font management software (e.g. Extensis Suitcase/Fusion). If the fonts are not vectorized and were not provided, it's normal the text on the Illustrator file doesn't look as it should.
The fonts could also be the ones from the Adobe Typekit. If you don't have an Adobe subscription, you might not be able to use them unless you subscribe to Typekit or find similar fonts to replace them.
Images and text disappearing
The way you are describing your issue with the images could be due to some "clipping masks." They can look like grouped objects but you don't ungroup clipping masks, you "release" them to remove them or edit them to modify them.
That's one reason why it's simpler to "link" back the original pictures rather than placing them again; at least they'll be re-inserted with their respective clipping mask if there's any, and at the exact position they should be.
Maybe have a look at the way your elements appear; the text could be in the background under your images.
You can always verify if something truly disappear by using the "command Y" or going in the menu "view" and selecting "outline." It should show you the outline of everything in your file. Go back in that same menu if you want to see your artboard as before, with the images.
I don't see why your text disappears if you embed images... I guess you mean you placed the Illustrator PDF file within an Illustrator .ai. Then no, I don't think you can edit your text; it didn't disappeared but it can't be edited in that form.
I can't really help on this part of your issue, I'll edit my answer if you can provide a small portion of the screenshot of your file! There's many ways to work with Illustrator and your friend could have created an effect with the text combined with the rasterized images; it's possible you won't be able to edit the file "easily."
But you should be able to make simple edit to any editable text if you have the fonts... and you should be able to see your images if you simply relink them to the original image files.