1. Added the text 'McKINNEY' onto a new layer, placed it over the old StJOHN'S text to match font, and then size and location (using free transform).
2. Sampled the colour of the other text on screen, to match the text colour.
3. Applied a lens blur to the text as a smart filter, reducing the transparently until it visually matched the other text on the screen (about 50% from memory)
4. Used the warp tool to slightly correct the shape of the text to match the perspective.
5. Added another layer and removed the original text
6. Moved the text a little bit to the right
Here's a link to the Photoshop (PSD) file with layers intact if anyone wants to improve further...
and the full size JPG