John, this is a good idea. I recommend all blood work, dating from the time you were first diagnosed to present. Next, reports of all the tests and scans that have been done: CT and MRI, X-rays, biopsies, EGD, etc. If you can obtain actual film of scans, it is helpful. However, it is done on a "loan" basis, as the facility that did the scans legally owns them. I have never heard of them put on CD, but in that case it would be a copy and okay to keep. Office visit notes are not necessary, unless you want them for your own edification. You would then likely need your doctor friend to interpret the medical jargon.
All of the above should be put together with the latest on top, going backwards in succession. I like Lucy's idea of filing the 3 categories separately.
In the first year or two after my diagnosis in '93, I kept all blood work results. Since it's now been 15 years since my initial diagnosis of hep C, I don't retain copies. When I go in for post-op visits following blood work, scans, or surgeries, they tell me the most important results. My blood work these days is very good, though of course the liver enzymes are always higher than normal. However, they've never been as high as 3x the upper limits of normal, which I was told is a red flag. Blood work is not always indicative of what is going on in the body; thus, the importance of scans. I do get operative reports and post-op visit notes.
If you have alpha fetoprotein done with your blood work, it would be good to keep copies of those, as it is a cancer marker. In my case, though, it never elevated much at all. Also, MRIs done with gadalinium contrast will also show cancer, so you definitely want those reports.
I hope this helps you.