Mary H.
First... what you have to do is decide how much of medical history is to be included...
Then...you'll have to decide on symbols you're going to use and their relevance... to keep track of certain conditions, and illnesses you'll have to decide which one are of most importance - to be visible on tree, and by color you might eventually depict extent of condition...
... toy around with Person's display properties and I'm sure you'll think of something...
The Legend is then easy. Right click and insert any legend from the menu. You'll see it's created from individuals as in your file (listed as "don't include in report")... You can edit it any way you like, change their layout and labes by them...!
For anything more elaborate you'll have to use custom tags and report generator...
If that's the case, I hope someone with more experience will find time to elaborate it here...
Best of luck!