The flowers are usually the most susceptible place for fireblight to enter the tree. With the flowers turning slightly black, it could be very early fireblight, or it could just be the flowers fading after pollination or non pollination.
I would pinch off the flowers either way. With the tree being so young and newly transplanted, letting fruit form will greatly weaken the tree, and it probably won't have
enough energy the first year to ripen the fruit, and if you pinch off the flowers it
should hopefully prevent the fireblight from spreading.
Bartlett is an extremely susceptible variety, and I just had to remove a large Bartlett because it never produced fruit because it got fireblight on its flowers so bad. I live in fireblight central though, so maybe it won't be as bad where you are. Fireblight resistance is one of the main things I look for now when looking at getting pear
trees. Seckel and Harrow Delight supposedly have good fireblight resistance and are high quality pears if you get another one.
Best of luck with your pear tree!
Steve