I have read a few posts about 3rd or 5th gear grinds when shifting quickly, isn't this car made to be sporty?

I'm looking to get a used 2003 g35 with only 25000KM on it, but I've noticed a 3rd gear grind which the seller advise will bring into Infiniti to fix, if Infiniti replaces the transmission will the car be ok after? Will quick shifting ever be a problem again?

 

I have an 03 6MT with 47,000+ miles (original owner), and I have never had a problem with grinding in any gear. Even shifting quickly. I would assume the transmission would be good to go if it were completely replaced. In theory it should be like new with no issues.