2005 Honda Foreman trx500fe gear snatching

Hi.. I have a problem with my 1st gear snatching on my quad. It means I can no longer use 1st so I must now try to fix it myself. I have applied myself to most quad issues but have no idea where to start and can find no videos concerning gear box problems.

Can someone please point me in the right direction. Its manual shift and I think perhaps its maybe just a cog worn but where.. ? I have to do this myself as I live in France and run my own farm.. and If I send it off to be fixed it probably won’t come back till next year!

Any advice is much appreciated. 🙂