FUE hair transplant, what is the likelihood of scarring?

All cuts on the skin will leave a scar.  FUE will leave a scar in the form of round "dots".   The color of your skin or hair color cannot predict how good or bad your scar may be.  If you shave your head, you will definitely see the FUE scars no matter how well you heal.

There are 2 procedures and each definitely produce scars. There is no such procedure that is scarless. It is important that you know that you may go completely bald in the next 5-6 years. This is extremely important as it is sets realistic expectations of what to expect. Typically you can cut your hair shorter with the Follicular Unit Extraction (FUE) procedure. For my FUE procedures, I use a 0.9mm punch. I also use a product called Acell which is growth factors derived from pig bladder. There are some case studies that demonstrate it promotes better wound healing. I use it in almost all my cases. Although this reduces the scarring, nevertheless, there is still scarring there. I have also developed a wrapping technique with Acell and Vaseline that actually promotes faster wound healing. I think the best thing to do is to see multiple doctors. I hope this helps. 
With regards to the scarring in the recipient area which is the area where the grafts are being transplanted into, this is rare but does depend on the instrument that is used. I use one times needles that are extremely sharp for every 50 sites that I create. This is very important because since the needles are very sharp, it does not actually create scarring. After every 50 sites, it becomes slight dull. This way I am able to minimize scarring in the recipient area.

Do your online research and then have multiple in-person consultations with hair transplant surgeons.  In cases such as yours, FUE may be the answer.  Alternatively, you may find out after these appointments that shaving your head and scalp micropigmentation (SMP) is the answer.  Are you agreeable to multiple procedures? How about lifetime maintenance/enhancement with oral finasteride &/or topical minoxidil &/or PRP?   There are so many individual issues to cover with each and every patient that you had better get well-informed before the first graft is taken.  If you so desire, my group has an office in mid-Wilshire that can answer all of these questions and more.  Best of luck to you.