Can a fever/sickness 17 days post-op change the end result?

If you are having fevers it is best to contact your doctor for a follow up.  You need an examination and possible treatment.

Fever in and of itself should not change your results unless the fever is from a significant scalp infection.If you have concerns about your scalp than return to your transplant surgeon.If your fever is from something unrelated than you shouldn't have a problem with your grafts.

If your fever is from something unrelated to the transplant (cold/flu, etc.) then your transplants should be fine. If it's accompanied by signs that point to an infection on your scalp (scalp redness, irritation, etc.) then that is something you need to see your doctor about in order to address.

Unless
you have a scalp infection causing your fever it is unlikely that the fever
will affect your grafts.   Your new hair grafts are set in their new
location by the end of the 4th day. 
If you are uncertain regarding your condition, return to your hair
transplant specialist for re-evaluation

A fever shouldn't effect the result of your transplant, provided it is not related to the procedure.  Please contact your physician if the fever doesn't subside or you are concerned of a infection on the scalp.

If you got a fever from (flu) then I doubt that the grafts will be impacted by the fever and illness you had