As my main interest is to produce accurately timed pulses for horological purposes, I am tempted to replace the 4 MH xtal with a 32768 watch xtal so that I can check my software on board. Is this likely to cause any poblems with the functioning of the board?
No, you can change the xtal. (max 20Mhz)
The 4 MHZ is choosen for general purpose examples but has no relation with the programming part of the K8048.