3rd gear grinding

I have a 2013 Kia soul Manual 120xxx miles. 3rd gear has been grinding for quite some time (I’m assuming the synchro went out) so I have just avoided it lol. I am now looking to sell the car and would like to fix or put in a new trans so i can sell for more. Couple questions

1. Is it worth paying to have the trans fixed should I get it replaced
2. If swapping the trans is the better option where is a trusted source for a used or new trans
3. If I’m swapping it how hard is the job?

TYIA