It turns out that the link to the PDF that is listed under the Parts section is broken. If you scroll down to the link below the Conclusion section you can download or open the PDF just fine. I’ll leave my question and answer up here in case anyone else has the issue.
Thanks for putting this guide together. I am having the same issue as Henry—if I click the View button next to “See Attached PDF” and then click on “Sega Game Gear Capacitor Replacement”, the website returns me to this guide instead of opening the PDF. Tried it in Edge and Chrome. Do you still have another copy of the guide available?