After eight years things are probably healed to the point that your risk of nipple necrosis is similar enough to that of the general population that most surgeons would be ok considering a nipple sparing mastectomy (as long as it is safe from the cancer perspective - something your general surgeon and oncologist would have to decide). If you were my patient and you were going to have an immediate reconstruction with implants I would probably use tissue expanders (which would be fully inflated at the time of surgery) temporarily just in case there was any skin breakdown to make sure the final result was not compromised. Best of Luck.
In theory, you have a higher chance that the nipple will have blood supply issues and not survive due to the anchor incision you had before. Besides, your nipple needs to be in the right location to consider a nipple sparing procedure. Your plastic surgeon should be able to advise you after an examination.
As far as removing the implants , it is a simple surgery which would most likely be done during the mastectomy. Nipple sparing is dependant on your nipple location and only your Plastic Surgeon can give you the best options once he or she examines you.