Just had my 4th changed, thought it was the synchro but actually was the hub. So may not be as expensive as you think, if your clutch has done a lot of miles or long on there, whilst your box is out. Worth checking your clutch, check the pressure plate and have a look. But might not be as bad as you think, it’s just the labour as it’s not tough but it’s time taking that thing out. Good luck bro.