Getting the circuit board out of the box is actually quite scary - it is a very tight fit. Even as an experienced electronics engineer I nearly changed my mind!
There's not much to grip at first - the best technique seemed to be to grip the VGA socket and wriggle the board gently from side to side until the board has come out enough to grip it by the edges. Then carry on wriggling the board from side to side and pulling gently until it's right out.
Once the board is out, changing J7 is exactly as shown. And the board then slips back into the case much more easily than it came out!