Dear Anna,
Boy does that sound familiar! Had similar issues with my father, including the pre-existing personality disorder. We were fortunate in two ways - he was receptive to observing some problems with remembering names and worried about it. Also, he used to be a professor and really respects teaching hospitals. So when I suggested we go see the doctors at a big teaching hospital to see if they could helps us with the memory/word finding problems, he agreed. He was fascinated by the process. Having a dx of Alzheimer's from them has not changed his denial about it one bit, however! It did help us to get clarity and be sure we were on the right treatment path. Hope that helps!