A few years ago I went on a gas boiler course to get the certificate to allow me to install and repair said items.
I paid for it and wasn't a plumber but did know the basics.
I found the so called tradesmen to be the dumbest group of learners id ever encountered. Reading the Sun and talking about football was all they were ever interested in.
Calculation of friction within a system to establish the correct diameter of pipe to use? Sod that, just use 22mm everywhere.
Fault finding on a rigged test boiler? You have 45 minutes to complete the task… five minutes in I was done with a functioning boiler.
Examining an installation to find defective and dangerous elements such as blocked flu or unsheathed pipes? There are ten things to find, I found fifteen, one of which the examiners did not know was there.
I would say you can replace the board yourself. Its not a gas fitting, does not involve any pipe work and will not interfere with combustion. Its only like replacing a room stat.
Replacing the boiler is an idiots solution, find a better plumber, if there is such a thing these days.
By the way I never used the gas cert I obtained for £2000, I was too conscientious and would have not done things fast or cheap enough to satisfy a firm so I stayed with my old job.
Moan over.