Synchro mesh

Hi all
I have an old disco. S reg petrol so she's 23 years old but only has 86000 miles on the clock and the rest of the engine is in good condition considering her age. the 1st gear is crunching going into 2nd. Does anyone have any rough ideas of how much this is likely to cost me to get put right, I've spoken to a garage and they have suggested to get a new refurbished gear box? Does this sound right or wrong? As you can't always trust a garage. Also is this something easily repaired if I was to just get the synchro mesh replaced and fitted by a mechanic. Which would be the cheaper and better option.
Thanks in advance.
Camodave

I’m sure this was asked in the last few days. Try the cheap fix first, which would be synthetic oil from difflock.com. The disco 1 box is known for this issue. My disco had 185k when I sold it, on the original gearbox. I used the synthetic oil which helped.

+1 my r380 responded well to mtf94 and it sorted some crunching i was getting. I am guessing it was full of ATF previously.